diff --git a/pkgs/development/interpreters/python/cpython/3.5/force_bytecode_determinism.patch b/pkgs/development/interpreters/python/cpython/3.5/force_bytecode_determinism.patch
new file mode 100644
index 00000000000..c263cdbff4d
--- /dev/null
+++ b/pkgs/development/interpreters/python/cpython/3.5/force_bytecode_determinism.patch
@@ -0,0 +1,17 @@
+--- a/Lib/py_compile.py
++++ b/Lib/py_compile.py
+@@ -139,3 +139,4 @@
+     source_stats = loader.path_stats(file)
++    source_mtime = 1 if 'DETERMINISTIC_BUILD' in os.environ else source_stats['mtime']
+     bytecode = importlib._bootstrap_external._code_to_bytecode(
+-            code, source_stats['mtime'], source_stats['size'])
++            code, source_mtime, source_stats['size'])
+--- a/Lib/importlib/_bootstrap_external.py
++++ b/Lib/importlib/_bootstrap_external.py
+@@ -485,5 +485,5 @@
+     if source_stats is not None:
+         try:
+-            source_mtime = int(source_stats['mtime'])
++            source_mtime = 1
+         except KeyError:
+             pass
diff --git a/pkgs/development/interpreters/python/cpython/default.nix b/pkgs/development/interpreters/python/cpython/default.nix
index 64021672276..7d90e201d19 100644
--- a/pkgs/development/interpreters/python/cpython/default.nix
+++ b/pkgs/development/interpreters/python/cpython/default.nix
@@ -87,6 +87,9 @@ in with passthru; stdenv.mkDerivation {
     # (since it will do a futile invocation of gcc (!) to find
     # libuuid, slowing down program startup a lot).
     (./. + "/${sourceVersion.major}.${sourceVersion.minor}/no-ldconfig.patch")
+  ] ++ optionals (isPy35 || isPy36) [
+    # Determinism: Write null timestamps when compiling python files.
+    ./3.5/force_bytecode_determinism.patch
   ] ++ optionals isPy35 [
     # Backports support for LD_LIBRARY_PATH from 3.6
     ./3.5/ld_library_path.patch
@@ -168,8 +171,8 @@ in with passthru; stdenv.mkDerivation {
     export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -msse2"
     export MACOSX_DEPLOYMENT_TARGET=10.6
   '' + optionalString (isPy3k && pythonOlder "3.7") ''
-    # Determinism: The interpreter is patched to write null timestamps when compiling python files.
-    # This way python does not try to update them when we freeze timestamps in nix store.
+    # Determinism: The interpreter is patched to write null timestamps when compiling Python files
+    #   so Python doesn't try to update the bytecode when seeing frozen timestamps in Nix's store.
     export DETERMINISTIC_BUILD=1;
   '' + optionalString stdenv.hostPlatform.isMusl ''
     export NIX_CFLAGS_COMPILE+=" -DTHREAD_STACK_SIZE=0x100000"