diff --git a/asm/eval.c b/asm/eval.c
index d8fe34ae..9ec093a0 100644
--- a/asm/eval.c
+++ b/asm/eval.c
@@ -746,7 +746,7 @@ static expr *eval_floatize(enum floatize type)
     return finishtemp();
 }
 
-static expr *eval_strfunc(enum strfunc type)
+static expr *eval_strfunc(enum strfunc type, const char *name)
 {
     char *string;
     size_t string_len;
@@ -760,13 +760,13 @@ static expr *eval_strfunc(enum strfunc type)
         scan();
     }
     if (tt != TOKEN_STR) {
-        nasm_nonfatal("expecting string");
+        nasm_nonfatal("expecting string as argument to %s", name);
         return NULL;
     }
     string_len = string_transform(tokval->t_charptr, tokval->t_inttwo,
                                   &string, type);
     if (string_len == (size_t)-1) {
-        nasm_nonfatal("invalid string for transform");
+        nasm_nonfatal("invalid input string to %s", name);
         return NULL;
     }
 
@@ -908,7 +908,7 @@ static expr *expr6(void)
         return eval_floatize(tokval->t_integer);
 
     case TOKEN_STRFUNC:
-        return eval_strfunc(tokval->t_integer);
+        return eval_strfunc(tokval->t_integer, tokval->t_charptr);
 
     case '(':
         scan();
diff --git a/asm/parser.c b/asm/parser.c
index 9f38844f..fce973b9 100644
--- a/asm/parser.c
+++ b/asm/parser.c
@@ -612,14 +612,14 @@ restart_parse:
                 if (i != TOKEN_STR) {
                     nasm_nonfatal("%s must be followed by a string constant",
                                   funcname);
-                        eop->type = EOT_NOTHING;
+                    eop->type = EOT_NOTHING;
                 } else {
                     eop->type = EOT_DB_STRING_FREE;
                     eop->stringlen =
                         string_transform(tokval.t_charptr, tokval.t_inttwo,
                                          &eop->stringval, func);
                     if (eop->stringlen == (size_t)-1) {
-                        nasm_nonfatal("invalid string for transform");
+                        nasm_nonfatal("invalid input string to %s", funcname);
                         eop->type = EOT_NOTHING;
                     }
                 }
diff --git a/travis/test/utf-error.stderr b/travis/test/utf-error.stderr
index 07ff4fb8..2d2caf1f 100644
--- a/travis/test/utf-error.stderr
+++ b/travis/test/utf-error.stderr
@@ -3,16 +3,16 @@
 ./travis/test/utf.asm:65: error: unterminated __utf16__ function
 ./travis/test/utf.asm:65: error: comma expected after operand 2
 ./travis/test/utf.asm:66: error: unterminated __utf16__ function
-./travis/test/utf.asm:67: error: invalid string for transform
+./travis/test/utf.asm:67: error: invalid input string to __utf16__
 ./travis/test/utf.asm:69: error: __utf16le__ must be followed by a string constant
 ./travis/test/utf.asm:70: error: __utf16le__ must be followed by a string constant
 ./travis/test/utf.asm:71: error: unterminated __utf16le__ function
 ./travis/test/utf.asm:71: error: comma expected after operand 2
 ./travis/test/utf.asm:72: error: unterminated __utf16le__ function
-./travis/test/utf.asm:73: error: invalid string for transform
+./travis/test/utf.asm:73: error: invalid input string to __utf16le__
 ./travis/test/utf.asm:75: error: __utf16be__ must be followed by a string constant
 ./travis/test/utf.asm:76: error: __utf16be__ must be followed by a string constant
 ./travis/test/utf.asm:77: error: unterminated __utf16be__ function
 ./travis/test/utf.asm:77: error: comma expected after operand 2
 ./travis/test/utf.asm:78: error: unterminated __utf16be__ function
-./travis/test/utf.asm:79: error: invalid string for transform
\ No newline at end of file
+./travis/test/utf.asm:79: error: invalid input string to __utf16be__