diff --git a/t/t4034/cpp/expect b/t/t4034/cpp/expect
index 3d37ddac42..b90b3f207b 100644
--- a/t/t4034/cpp/expect
+++ b/t/t4034/cpp/expect
@@ -7,15 +7,15 @@ Foo() : x(0<RED>&&1<RESET><GREEN>&42<RESET>) { <RED>foo0<RESET><GREEN>bar<RESET>
 cout<<"Hello World<RED>!<RESET><GREEN>?<RESET>\n"<<endl;
 <GREEN>(<RESET>1 <RED>-<RESET><GREEN>+<RESET>1e10 0xabcdef<GREEN>)<RESET> '<RED>x<RESET><GREEN>.<RESET>'
 // long double<RESET>
-3.141'592'<RED>653e-10l<RESET><GREEN>654e+10l<RESET>
+<RED>3.141'592'653e-10l<RESET><GREEN>3.141'592'654e+10l<RESET>
 // float<RESET>
 <RED>120E5f<RESET><GREEN>120E6f<RESET>
 // hex<RESET>
-0xdead'<RED>beaf<RESET><GREEN>Beaf<RESET>+<RED>8ULL<RESET><GREEN>7ULL<RESET>
+<RED>0xdead'beaf<RESET><GREEN>0xdead'Beaf<RESET>+<RED>8ULL<RESET><GREEN>7ULL<RESET>
 // octal<RESET>
-0123'<RED>4567<RESET><GREEN>4560<RESET>
+<RED>0123'4567<RESET><GREEN>0123'4560<RESET>
 // binary<RESET>
-<RED>0b10<RESET><GREEN>0b11<RESET>'00+e1
+<RED>0b10'00<RESET><GREEN>0b11'00<RESET>+e1
 // expression<RESET>
 1.5-e+<RED>2<RESET><GREEN>3<RESET>+f
 // another one<RESET>
diff --git a/userdiff.c b/userdiff.c
index 8b49194f56..c1084650dd 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -67,11 +67,11 @@ PATTERNS("cpp",
 	 /* identifiers and keywords */
 	 "[a-zA-Z_][a-zA-Z0-9_]*"
 	 /* decimal and octal integers as well as floatingpoint numbers */
-	 "|[0-9][0-9.]*([Ee][-+]?[0-9]+)?[fFlLuU]*"
+	 "|[0-9][0-9.']*([Ee][-+]?[0-9]+)?[fFlLuU]*"
 	 /* hexadecimal and binary integers */
-	 "|0[xXbB][0-9a-fA-F]+[lLuU]*"
+	 "|0[xXbB][0-9a-fA-F']+[lLuU]*"
 	 /* floatingpoint numbers that begin with a decimal point */
-	 "|\\.[0-9]+([Ee][-+]?[0-9]+)?[fFlL]?"
+	 "|\\.[0-9][0-9']*([Ee][-+]?[0-9]+)?[fFlL]?"
 	 "|[-+*/<>%&^|=!]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\||::|->\\*?|\\.\\*"),
 PATTERNS("csharp",
 	 /* Keywords */