diff --git a/core/ustring.cpp b/core/ustring.cpp
index 2c294e7a878..a57fd8b171e 100644
--- a/core/ustring.cpp
+++ b/core/ustring.cpp
@@ -1706,9 +1706,7 @@ String::String(const StrRange &p_range) {
 
 int String::hex_to_int(bool p_with_prefix) const {
 	int len = length();
-	if (len == 0 || (p_with_prefix && len < 3)) {
-		return 0;
-	}
+	ERR_FAIL_COND_V_MSG(p_with_prefix ? len < 3 : len == 0, 0, String("Invalid hexadecimal notation length in string ") + (p_with_prefix ? "with" : "without") + " prefix \"" + *this + "\".");
 
 	const CharType *s = ptr();
 
@@ -1719,9 +1717,7 @@ int String::hex_to_int(bool p_with_prefix) const {
 	}
 
 	if (p_with_prefix) {
-		if (s[0] != '0' || s[1] != 'x') {
-			return 0;
-		}
+		ERR_FAIL_COND_V_MSG(s[0] != '0' || LOWERCASE(s[1]) != 'x', 0, "Invalid hexadecimal notation prefix in string \"" + *this + "\".");
 		s += 2;
 	}
 
@@ -1735,7 +1731,7 @@ int String::hex_to_int(bool p_with_prefix) const {
 		} else if (c >= 'a' && c <= 'f') {
 			n = (c - 'a') + 10;
 		} else {
-			return 0;
+			ERR_FAIL_V_MSG(0, "Invalid hexadecimal notation character \"" + chr(*s) + "\" in string \"" + *this + "\".");
 		}
 		// Check for overflow/underflow, with special case to ensure INT32_MIN does not result in error
 		bool overflow = ((hex > INT32_MAX / 16) && (sign == 1 || (sign == -1 && hex != (INT32_MAX >> 4) + 1))) || (sign == -1 && hex == (INT32_MAX >> 4) + 1 && c > '0');
@@ -1749,9 +1745,8 @@ int String::hex_to_int(bool p_with_prefix) const {
 }
 
 int64_t String::hex_to_int64(bool p_with_prefix) const {
-	if (p_with_prefix && length() < 3) {
-		return 0;
-	}
+	int len = length();
+	ERR_FAIL_COND_V_MSG(p_with_prefix ? len < 3 : len == 0, 0, String("Invalid hexadecimal notation length in string ") + (p_with_prefix ? "with" : "without") + " prefix \"" + *this + "\".");
 
 	const CharType *s = ptr();
 
@@ -1762,9 +1757,7 @@ int64_t String::hex_to_int64(bool p_with_prefix) const {
 	}
 
 	if (p_with_prefix) {
-		if (s[0] != '0' || s[1] != 'x') {
-			return 0;
-		}
+		ERR_FAIL_COND_V_MSG(s[0] != '0' || LOWERCASE(s[1]) != 'x', 0, "Invalid hexadecimal notation prefix in string \"" + *this + "\".");
 		s += 2;
 	}
 
@@ -1778,7 +1771,7 @@ int64_t String::hex_to_int64(bool p_with_prefix) const {
 		} else if (c >= 'a' && c <= 'f') {
 			n = (c - 'a') + 10;
 		} else {
-			return 0;
+			ERR_FAIL_V_MSG(0, "Invalid hexadecimal notation character \"" + chr(*s) + "\" in string \"" + *this + "\".");
 		}
 		bool overflow = ((hex > INT64_MAX / 16) && (sign == 1 || (sign == -1 && hex != (INT64_MAX >> 4) + 1))) || (sign == -1 && hex == (INT64_MAX >> 4) + 1 && c > '0');
 		ERR_FAIL_COND_V_MSG(overflow, sign == 1 ? INT64_MAX : INT64_MIN, "Cannot represent " + *this + " as a 64-bit signed integer, since the value is " + (sign == 1 ? "too large." : "too small."));