1 files changed, 3 insertions, 1 deletions
diff --git a/core/src/fpdftext/fpdf_text.cpp b/core/src/fpdftext/fpdf_text.cpp
index e9ad338025..9ecbc21bda 100644
--- a/core/src/fpdftext/fpdf_text.cpp
+++ b/core/src/fpdftext/fpdf_text.cpp
@@ -436,8 +436,10 @@ void NormalizeString(CFX_WideString& str) {
 static FX_BOOL IsNumber(CFX_WideString& str) {
   for (int i = 0; i < str.GetLength(); i++) {
     FX_WCHAR ch = str[i];
-    if (!std::isdigit(ch) && ch != '-' && ch != '+' && ch != '.' && ch != ' ')
+    if ((ch < '0' || ch > '9') && ch != '-' && ch != '+' && ch != '.' &&
+        ch != ' ') {
       return FALSE;
+    }
   }
   return TRUE;
 }