diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 946c6201106..8d48b5a8cd2 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-11  Alan Modra  <amodra@gmail.com>
+
+	* h8300-dis.c (extract_immediate): Avoid signed overflow.
+	(bfd_h8_disassemble): Likewise.
+
 2019-12-11  Alan Modra  <amodra@gmail.com>
 
 	* d30v-dis.c (print_insn): Make opind unsigned.  Don't access
diff --git a/opcodes/h8300-dis.c b/opcodes/h8300-dis.c
index 75d429e6204..c99b9f34989 100644
--- a/opcodes/h8300-dis.c
+++ b/opcodes/h8300-dis.c
@@ -140,7 +140,8 @@ extract_immediate (FILE *stream,
       break;
     case L_32:
       *len = 32;
-      *cst = (data[0] << 24) + (data[1] << 16) + (data[2] << 8) + data[3];
+      *cst = (((unsigned) data[0] << 24) + (data[1] << 16)
+	      + (data[2] << 8) + data[3]);
       break;
     default:
       *len = 0;
@@ -530,7 +531,7 @@ bfd_h8_disassemble (bfd_vma addr, disassemble_info *info, int mach)
 		{
 		  int i = len / 2;
 
-		  cst[opnr] = ((data[i] << 24)
+		  cst[opnr] = (((unsigned) data[i] << 24)
 			       | (data[i + 1] << 16)
 			       | (data[i + 2] << 8)
 			       | (data[i + 3]));