--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -641,6 +641,19 @@ get_lambda_name(void)
     return name;
 }
 
+/*
+ * Allocate a "ufunc_T" for a function called "name".
+ * Makes sure the size is right.
+ */
+    static ufunc_T *
+alloc_ufunc(char_u *name)
+{
+    // When the name is short we need to make sure we allocate enough bytes for
+    // the whole struct, including any padding.
+    size_t len = offsetof(ufunc_T, uf_name) + STRLEN(name) + 1;
+    return alloc_clear(len < sizeof(ufunc_T) ? sizeof(ufunc_T) : len);
+}
+
 #if defined(FEAT_LUA) || defined(PROTO)
 /*
  * Registers a native C callback which can be called from Vim script.
@@ -652,7 +665,7 @@ register_cfunc(cfunc_T cb, cfunc_free_T 
     char_u	*name = get_lambda_name();
     ufunc_T	*fp;
 
-    fp = alloc_clear(offsetof(ufunc_T, uf_name) + STRLEN(name) + 1);
+    fp = alloc_ufunc(name);
     if (fp == NULL)
 	return NULL;
 
@@ -1356,7 +1369,7 @@ lambda_function_body(
     }
 
     name = get_lambda_name();
-    ufunc = alloc_clear(offsetof(ufunc_T, uf_name) + STRLEN(name) + 1);
+    ufunc = alloc_ufunc(name);
     if (ufunc == NULL)
 	goto erret;
     set_ufunc_name(ufunc, name);
@@ -1557,7 +1570,7 @@ get_lambda_tv(
 	char_u	    *line_end;
 	char_u	    *name = get_lambda_name();
 
-	fp = alloc_clear(offsetof(ufunc_T, uf_name) + STRLEN(name) + 1);
+	fp = alloc_ufunc(name);
 	if (fp == NULL)
 	    goto errret;
 	fp->uf_def_status = UF_NOT_COMPILED;
@@ -2558,7 +2571,7 @@ copy_lambda_to_global_func(
 	return FAIL;
     }
 
-    fp = alloc_clear(offsetof(ufunc_T, uf_name) + STRLEN(global) + 1);
+    fp = alloc_ufunc(global);
     if (fp == NULL)
 	return FAIL;
 
@@ -5081,7 +5094,7 @@ define_function(
 	    }
 	}
 
-	fp = alloc_clear(offsetof(ufunc_T, uf_name) + STRLEN(name) + 1);
+	fp = alloc_ufunc(name);
 	if (fp == NULL)
 	    goto erret;
 	fp_allocated = TRUE;
@@ -5525,10 +5538,7 @@ get_user_func_name(expand_T *xp, int idx
     ufunc_T *
 copy_function(ufunc_T *fp)
 {
-    // The struct may have padding, make sure we allocate at least the size of
-    // the struct.
-    size_t len = offsetof(ufunc_T, uf_name) + STRLEN(fp->uf_name) + 1;
-    ufunc_T *ufunc = alloc_clear(len < sizeof(ufunc_T) ? sizeof(ufunc_T) : len);
+    ufunc_T *ufunc = alloc_ufunc(fp->uf_name);
     if (ufunc == NULL)
 	return NULL;