diff --git a/src/libsysprof-analyze/sysprof-document-frame-private.h b/src/libsysprof-analyze/sysprof-document-frame-private.h
index 96949ac4..91a74a8a 100644
--- a/src/libsysprof-analyze/sysprof-document-frame-private.h
+++ b/src/libsysprof-analyze/sysprof-document-frame-private.h
@@ -81,8 +81,8 @@ SysprofDocumentFrame *_sysprof_document_frame_new (GMappedFile               *ma
 #endif
 
 static inline const char *
-SYSPROF_DOCUMENT_FRAME_CSTRING (SysprofDocumentFrame *self,
-                                const char           *str)
+_SYSPROF_DOCUMENT_FRAME_CSTRING (SysprofDocumentFrame *self,
+                                 const char           *str)
 {
   const char *endptr = (const char *)self->frame + self->frame_len;
 
@@ -95,4 +95,7 @@ SYSPROF_DOCUMENT_FRAME_CSTRING (SysprofDocumentFrame *self,
   return NULL;
 }
 
+#define SYSPROF_DOCUMENT_FRAME_CSTRING(obj,str) \
+  _SYSPROF_DOCUMENT_FRAME_CSTRING(SYSPROF_DOCUMENT_FRAME(obj),str)
+
 G_END_DECLS
diff --git a/src/libsysprof-analyze/sysprof-document-mmap.c b/src/libsysprof-analyze/sysprof-document-mmap.c
index 8a5c99e3..c5a2f85c 100644
--- a/src/libsysprof-analyze/sysprof-document-mmap.c
+++ b/src/libsysprof-analyze/sysprof-document-mmap.c
@@ -180,5 +180,5 @@ sysprof_document_mmap_get_file (SysprofDocumentMmap *self)
 
   mmap = SYSPROF_DOCUMENT_FRAME_GET (self, SysprofCaptureMap);
 
-  return SYSPROF_DOCUMENT_FRAME_CSTRING (SYSPROF_DOCUMENT_FRAME (self), mmap->filename);
+  return SYSPROF_DOCUMENT_FRAME_CSTRING (self, mmap->filename);
 }