diff --git a/dtool/LocalSetup.cmake b/dtool/LocalSetup.cmake
index a8cee40f6c..d153e465b9 100644
--- a/dtool/LocalSetup.cmake
+++ b/dtool/LocalSetup.cmake
@@ -34,7 +34,7 @@ int main(int argc, char *argv[]) { fs.open(\"file\", std::fstream::out, 0644); r
 check_cxx_source_compiles("
 #include <unistd.h>
 int main(int argc, char *argv[]) { lockf(0, F_LOCK, 0); return 0; }
-" HAVE_LOCKF)
+" PHAVE_LOCKF)
 
 # Check if we have a wchar_t type.
 check_type_size(wchar_t HAVE_WCHAR_T)
diff --git a/dtool/dtool_config.h.in b/dtool/dtool_config.h.in
index 19d5408c37..165acc4636 100644
--- a/dtool/dtool_config.h.in
+++ b/dtool/dtool_config.h.in
@@ -262,7 +262,7 @@
 #cmakedefine HAVE_OPEN_MASK
 
 /* Define if we have a lockf() function. */
-#cmakedefine HAVE_LOCKF
+#cmakedefine PHAVE_LOCKF
 
 /* Define if some header file defines wchar_t. */
 #cmakedefine HAVE_WCHAR_T