diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 12609e2dcb6..97453f04c05 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2000-08-08  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* c-lex.c (yylex): Don't allow integer suffixes 'LUL', 'Ll', 'lL'.
+
 2000-08-07  Nick Clifton  <nickc@redhat.com>
 
 	* config/mips/mips.c: Fix compile time warning messages.
diff --git a/gcc/c-lex.c b/gcc/c-lex.c
index 616ecbe2080..e0137e32ae0 100644
--- a/gcc/c-lex.c
+++ b/gcc/c-lex.c
@@ -1762,6 +1762,7 @@ yylex ()
 	    int spec_unsigned = 0;
 	    int spec_long = 0;
 	    int spec_long_long = 0;
+	    int suffix_lu = 0;
 	    int spec_imag = 0;
 	    int warn = 0, i;
 
@@ -1773,6 +1774,8 @@ yylex ()
 		    if (spec_unsigned)
 		      error ("two `u's in integer constant");
 		    spec_unsigned = 1;
+		    if (spec_long)
+		      suffix_lu = 1;
 		  }
 		else if (c == 'l' || c == 'L')
 		  {
@@ -1780,12 +1783,16 @@ yylex ()
 		      {
 			if (spec_long_long)
 			  error ("three `l's in integer constant");
+			else if (suffix_lu)
+			  error ("`LUL' is not a valid integer suffix");
+			else if (c != spec_long)
+			  error ("`Ll' and `lL' are not valid integer suffixes");
 			else if (pedantic && ! flag_isoc99
 				 && ! in_system_header && warn_long_long)
 			  pedwarn ("ANSI C forbids long long integer constants");
 			spec_long_long = 1;
 		      }
-		    spec_long = 1;
+		    spec_long = c;
 		  }
 		else if (c == 'i' || c == 'j' || c == 'I' || c == 'J')
 		  {
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f50a8de7c20..febc005df0c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2000-08-08  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* gcc.dg/noncompile/const-ll-1.c: New test.
+
 2000-08-07  Joseph S. Myers  <jsm28@cam.ac.uk>
 
 	* gcc.dg/c90-printf-2.c, gcc.dg/c99-printf-2.c: New tests.
diff --git a/gcc/testsuite/gcc.dg/noncompile/const-ll-1.c b/gcc/testsuite/gcc.dg/noncompile/const-ll-1.c
new file mode 100644
index 00000000000..e38dff2b752
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/noncompile/const-ll-1.c
@@ -0,0 +1,24 @@
+/* Test for broken long long suffixes.  */
+/* Origin: Joseph Myers <jsm28@cam.ac.uk> */
+
+/* The following are valid integer suffixes, according to C99:
+
+   no suffix
+   u or U
+   ul, uL, Ul or UL
+   ull, uLL, Ull or ULL
+   l or L
+   lu, lU, Lu or LU
+   llu, llU, LLu or LLU
+
+   The following are not but have been accepted by GCC in the past:
+
+   lul and case variants (the 'l's being separated by a 'u')
+   lL, Ll and variants with a 'u' (mixed case pair of 'l's)
+
+   (cpplib gets this right when processing #if expressions.)
+
+*/
+
+unsigned long long a = 1LUL; /* { dg-error "LUL" "error for LUL suffix" } */
+long long b = 1Ll; /* { dg-error "Ll" "error for Ll suffix" } */