diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 67fef190920..6d8bfc19b1e 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -127,14 +127,9 @@ ref<EvalState> EvalCommand::getEvalState()
 {
     if (!evalState) {
         evalState =
-            #if HAVE_BOEHMGC
             std::allocate_shared<EvalState>(
                 traceable_allocator<EvalState>(),
-            #else
-            std::make_shared<EvalState>(
-            #endif
-                lookupPath, getEvalStore(), fetchSettings, evalSettings, getStore())
-            ;
+                lookupPath, getEvalStore(), fetchSettings, evalSettings, getStore());
 
         evalState->repair = repair;
 
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 46b6fbadc02..940b16dfdfd 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -29,11 +29,6 @@
 #include "ref.hh"
 #include "value.hh"
 
-#if HAVE_BOEHMGC
-#define GC_INCLUDE_NEW
-#include <gc/gc_cpp.h>
-#endif
-
 #include "strings.hh"
 
 namespace nix {
@@ -62,9 +57,7 @@ enum class ProcessLineResult {
 struct NixRepl
     : AbstractNixRepl
     , detail::ReplCompleterMixin
-    #if HAVE_BOEHMGC
     , gc
-    #endif
 {
     size_t debugTraceIndex;
 
diff --git a/src/libexpr-c/nix_api_external.cc b/src/libexpr-c/nix_api_external.cc
index fa78eb5df39..d673bcb0b30 100644
--- a/src/libexpr-c/nix_api_external.cc
+++ b/src/libexpr-c/nix_api_external.cc
@@ -14,12 +14,6 @@
 
 #include <nlohmann/json.hpp>
 
-#if HAVE_BOEHMGC
-# include "gc/gc.h"
-# define GC_INCLUDE_NEW 1
-# include "gc_cpp.h"
-#endif
-
 void nix_set_string_return(nix_string_return * str, const char * c)
 {
     str->str = c;
diff --git a/src/libexpr-c/nix_api_value.cc b/src/libexpr-c/nix_api_value.cc
index fa2a9cbe2ae..bae078d312f 100644
--- a/src/libexpr-c/nix_api_value.cc
+++ b/src/libexpr-c/nix_api_value.cc
@@ -14,12 +14,6 @@
 #include "nix_api_value.h"
 #include "value/context.hh"
 
-#if HAVE_BOEHMGC
-#  include "gc/gc.h"
-#  define GC_INCLUDE_NEW 1
-#  include "gc_cpp.h"
-#endif
-
 // Internal helper functions to check [in] and [out] `Value *` parameters
 static const nix::Value & check_value_not_null(const nix_value * value)
 {
diff --git a/src/libexpr/eval-gc.hh b/src/libexpr/eval-gc.hh
index 005175eb78d..1be9ff65b57 100644
--- a/src/libexpr/eval-gc.hh
+++ b/src/libexpr/eval-gc.hh
@@ -3,6 +3,32 @@
 
 #include <cstddef>
 
+#if HAVE_BOEHMGC
+
+#  define GC_INCLUDE_NEW
+
+#  include <gc/gc.h>
+#  include <gc/gc_cpp.h>
+#  include <gc/gc_allocator.h>
+
+#else
+
+/* Some dummy aliases for Boehm GC definitions to reduce the number of
+   #ifdefs. */
+
+template<typename T>
+using traceable_allocator = std::allocator<T>;
+
+template<typename T>
+using gc_allocator = std::allocator<T>;
+
+#  define GC_MALLOC_ATOMIC std::malloc
+#  define GC_STRDUP std::strdup
+struct gc
+{};
+
+#endif
+
 namespace nix {
 
 /**
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2420f15c19a..379839ce32f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1,5 +1,4 @@
 #include "eval.hh"
-#include "eval-gc.hh"
 #include "eval-settings.hh"
 #include "primops.hh"
 #include "print-options.hh"
@@ -39,16 +38,6 @@
 #  include <sys/resource.h>
 #endif
 
-#if HAVE_BOEHMGC
-
-#  define GC_INCLUDE_NEW
-
-#  include <gc/gc.h>
-#  include <gc/gc_cpp.h>
-#  include <gc/gc_allocator.h>
-
-#endif
-
 #include "strings-inline.hh"
 
 using json = nlohmann::json;
@@ -58,11 +47,7 @@ namespace nix {
 static char * allocString(size_t size)
 {
     char * t;
-#if HAVE_BOEHMGC
     t = (char *) GC_MALLOC_ATOMIC(size);
-#else
-    t = (char *) malloc(size);
-#endif
     if (!t) throw std::bad_alloc();
     return t;
 }
@@ -71,11 +56,7 @@ static char * allocString(size_t size)
 static char * dupString(const char * s)
 {
     char * t;
-#if HAVE_BOEHMGC
     t = GC_STRDUP(s);
-#else
-    t = strdup(s);
-#endif
     if (!t) throw std::bad_alloc();
     return t;
 }
@@ -99,11 +80,7 @@ static const char * makeImmutableString(std::string_view s)
 
 RootValue allocRootValue(Value * v)
 {
-#if HAVE_BOEHMGC
     return std::allocate_shared<Value *>(traceable_allocator<Value *>(), v);
-#else
-    return std::make_shared<Value *>(v);
-#endif
 }
 
 // Pretty print types for assertion errors
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index da9dd2087ca..f7ed6be83af 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -139,11 +139,7 @@ struct Constant
     bool impureOnly = false;
 };
 
-#if HAVE_BOEHMGC
-    typedef std::map<std::string, Value *, std::less<std::string>, traceable_allocator<std::pair<const std::string, Value *> > > ValMap;
-#else
-    typedef std::map<std::string, Value *> ValMap;
-#endif
+typedef std::map<std::string, Value *, std::less<std::string>, traceable_allocator<std::pair<const std::string, Value *> > > ValMap;
 
 typedef std::unordered_map<PosIdx, DocComment> DocCommentMap;
 
@@ -329,21 +325,13 @@ private:
     /**
      * A cache from path names to parse trees.
      */
-#if HAVE_BOEHMGC
     typedef std::unordered_map<SourcePath, Expr *, std::hash<SourcePath>, std::equal_to<SourcePath>, traceable_allocator<std::pair<const SourcePath, Expr *>>> FileParseCache;
-#else
-    typedef std::unordered_map<SourcePath, Expr *> FileParseCache;
-#endif
     FileParseCache fileParseCache;
 
     /**
      * A cache from path names to values.
      */
-#if HAVE_BOEHMGC
     typedef std::unordered_map<SourcePath, Value, std::hash<SourcePath>, std::equal_to<SourcePath>, traceable_allocator<std::pair<const SourcePath, Value>>> FileEvalCache;
-#else
-    typedef std::unordered_map<SourcePath, Value> FileEvalCache;
-#endif
     FileEvalCache fileEvalCache;
 
     /**
diff --git a/src/libexpr/gc-small-vector.hh b/src/libexpr/gc-small-vector.hh
index 7f4f08fc753..8330dd2dca1 100644
--- a/src/libexpr/gc-small-vector.hh
+++ b/src/libexpr/gc-small-vector.hh
@@ -2,28 +2,15 @@
 
 #include <boost/container/small_vector.hpp>
 
-#if HAVE_BOEHMGC
-
-#include <gc/gc.h>
-#include <gc/gc_cpp.h>
-#include <gc/gc_allocator.h>
-
-#endif
+#include "value.hh"
 
 namespace nix {
 
-struct Value;
-
 /**
  * A GC compatible vector that may used a reserved portion of `nItems` on the stack instead of allocating on the heap.
  */
-#if HAVE_BOEHMGC
 template <typename T, size_t nItems>
 using SmallVector = boost::container::small_vector<T, nItems, traceable_allocator<T>>;
-#else
-template <typename T, size_t nItems>
-using SmallVector = boost::container::small_vector<T, nItems>;
-#endif
 
 /**
  * A vector of value pointers. See `SmallVector`.
@@ -39,4 +26,4 @@ using SmallValueVector = SmallVector<Value *, nItems>;
 template <size_t nItems>
 using SmallTemporaryValueVector = SmallVector<Value, nItems>;
 
-}
\ No newline at end of file
+}
diff --git a/src/libexpr/get-drvs.hh b/src/libexpr/get-drvs.hh
index db3eedb05c7..e4e277af8cc 100644
--- a/src/libexpr/get-drvs.hh
+++ b/src/libexpr/get-drvs.hh
@@ -83,11 +83,7 @@ public:
 };
 
 
-#if HAVE_BOEHMGC
 typedef std::list<PackageInfo, traceable_allocator<PackageInfo>> PackageInfos;
-#else
-typedef std::list<PackageInfo> PackageInfos;
-#endif
 
 
 /**
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8d53a1dfd71..7b6f222a8d9 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -631,11 +631,7 @@ struct CompareValues
 };
 
 
-#if HAVE_BOEHMGC
 typedef std::list<Value *, gc_allocator<Value *>> ValueList;
-#else
-typedef std::list<Value *> ValueList;
-#endif
 
 
 static Bindings::const_iterator getAttr(
@@ -3136,11 +3132,7 @@ static void prim_zipAttrsWith(EvalState & state, const PosIdx pos, Value * * arg
         std::optional<ListBuilder> list;
     };
 
-#if HAVE_BOEHMGC
     std::map<Symbol, Item, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, Item>>> attrsSeen;
-#else
-    std::map<Symbol, Item> attrsSeen;
-#endif
 
     state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.zipAttrsWith");
     state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.zipAttrsWith");
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index f68befe0e81..0ffe74dabf1 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -4,15 +4,13 @@
 #include <cassert>
 #include <span>
 
+#include "eval-gc.hh"
 #include "symbol-table.hh"
 #include "value/context.hh"
 #include "source-path.hh"
 #include "print-options.hh"
 #include "checked-arithmetic.hh"
 
-#if HAVE_BOEHMGC
-#include <gc/gc_allocator.h>
-#endif
 #include <nlohmann/json_fwd.hpp>
 
 namespace nix {
@@ -498,15 +496,9 @@ void Value::mkBlackhole()
 }
 
 
-#if HAVE_BOEHMGC
 typedef std::vector<Value *, traceable_allocator<Value *>> ValueVector;
 typedef std::unordered_map<Symbol, Value *, std::hash<Symbol>, std::equal_to<Symbol>, traceable_allocator<std::pair<const Symbol, Value *>>> ValueMap;
 typedef std::map<Symbol, ValueVector, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, ValueVector>>> ValueVectorMap;
-#else
-typedef std::vector<Value *> ValueVector;
-typedef std::unordered_map<Symbol, Value *> ValueMap;
-typedef std::map<Symbol, ValueVector> ValueVectorMap;
-#endif
 
 
 /**
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 34de79ac877..7a9516d5ed9 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -2,7 +2,6 @@
 #include "current-process.hh"
 #include "command.hh"
 #include "common-args.hh"
-#include "eval-gc.hh"
 #include "eval.hh"
 #include "eval-settings.hh"
 #include "globals.hh"