diff --git a/src/common.c b/src/common.c
index 566df0f44..4ce440a51 100644
--- a/src/common.c
+++ b/src/common.c
@@ -368,6 +368,9 @@ bool parse_value(type_t type, const char *str, parsed_value_t *value)
             *p = toupper_iso88591(*p);
          *p = '\0';
 
+         if (p == copy)
+            return false;
+
          ident_t id = ident_new(copy);
 
          value->integer = -1;
diff --git a/test/test_value.c b/test/test_value.c
index d8688f6f0..e29b10aae 100644
--- a/test/test_value.c
+++ b/test/test_value.c
@@ -180,6 +180,8 @@ START_TEST(test_physical)
 
    fail_unless(parse_value(t, " 3   ps ", &v));
    ck_assert_int_eq(v.integer, 3000);
+
+   fail_if(parse_value(t, " 5", &v));
 }
 END_TEST