diff --git a/CHANGES.current b/CHANGES.current
index 1f0dd3807..b0488780c 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -7,6 +7,9 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-07-25: olly
+	    Support for C++14 binary integer literals in preprocessor expressions.
+
 2022-07-20: wsfulton
             [C#, Java] Ensure the order of interfaces generated in proxy interfaces for the
             %interface family of macros is the same as that parsed from the bases in C++.
diff --git a/Examples/test-suite/cpp14_binary_integer_literals.i b/Examples/test-suite/cpp14_binary_integer_literals.i
index 5e736be64..54e070032 100644
--- a/Examples/test-suite/cpp14_binary_integer_literals.i
+++ b/Examples/test-suite/cpp14_binary_integer_literals.i
@@ -1,5 +1,9 @@
 %module cpp14_binary_integer_literals
 
+#if 0b100 < 4
+# error binary constant in preprocessor expression failed
+#endif
+
 %inline %{
 int b1 = 0b1;
 int b2 = 0b10;
diff --git a/Source/Preprocessor/expr.c b/Source/Preprocessor/expr.c
index 52e467b6c..15bf99657 100644
--- a/Source/Preprocessor/expr.c
+++ b/Source/Preprocessor/expr.c
@@ -318,7 +318,12 @@ int Preprocessor_expr(DOH *s, int *error) {
       if ((token == SWIG_TOKEN_INT) || (token == SWIG_TOKEN_UINT) || (token == SWIG_TOKEN_LONG) || (token == SWIG_TOKEN_ULONG)) {
 	/* A number.  Reduce EXPR_TOP to an EXPR_VALUE */
 	char *c = Char(Scanner_text(scan));
-	stack[sp].value = (long) strtol(c, 0, 0);
+	if (c[0] == '0' && (c[1] == 'b' || c[1] == 'B')) {
+	  // strtol() doesn't handle binary constants.
+	  stack[sp].value = (long) strtol(c + 2, 0, 2);
+	} else {
+	  stack[sp].value = (long) strtol(c, 0, 0);
+	}
 	stack[sp].svalue = 0;
 	stack[sp].op = EXPR_VALUE;
       } else if ((token == SWIG_TOKEN_MINUS) || (token == SWIG_TOKEN_PLUS) || (token == SWIG_TOKEN_LNOT) || (token == SWIG_TOKEN_NOT)) {