diff --git a/Source/cmFileCommand.cxx b/Source/cmFileCommand.cxx
index e39630eb63..4c288f5f21 100644
--- a/Source/cmFileCommand.cxx
+++ b/Source/cmFileCommand.cxx
@@ -10,6 +10,7 @@
 
 #include <algorithm>
 #include <assert.h>
+#include <ctype.h>
 #include <memory> // IWYU pragma: keep
 #include <sstream>
 #include <stdio.h>
@@ -609,8 +610,8 @@ bool cmFileCommand::HandleStringsCommand(std::vector<std::string> const& args)
       continue;
     }
 
-    if ((c >= 0x20 && c < 0x7F) || c == '\t' ||
-        (c == '\n' && newline_consume)) {
+    if (c >= 0 && c <= 0xFF &&
+        (isprint(c) || c == '\t' || (c == '\n' && newline_consume))) {
       // This is an ASCII character that may be part of a string.
       // Cast added to avoid compiler warning. Cast is ok because
       // c is guaranteed to fit in char by the above if...