diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ac84245c34..df8488b109 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-08-23  Sandra Loosemore  <sandra@codesourcery.com>
+
+	* nios2-tdep.c (struct reg_value): Improve comments.  Make
+	the offset field signed.
+
 2019-08-22  Christian Biesinger  <cbiesinger@google.com>
 
 	* python/lib/gdb/__init__.py (_execute_file): New function.
diff --git a/gdb/nios2-tdep.c b/gdb/nios2-tdep.c
index 2a21c33b83..8d685d4aca 100644
--- a/gdb/nios2-tdep.c
+++ b/gdb/nios2-tdep.c
@@ -58,13 +58,15 @@ static int nios2_debug = 0;
    analysis; see the reg_value and reg_saved tables in
    struct nios2_unwind_cache, respectively.  */
 
-/* struct reg_value is used to record that a register has the same value
-   as reg at the given offset from the start of a function.  */
+/* struct reg_value is used to record that a register has reg's initial
+   value at the start of a function plus the given constant offset.
+   If reg == 0, then the value is just the offset.
+   If reg < 0, then the value is unknown.  */
 
 struct reg_value
 {
   int reg;
-  unsigned int offset;
+  int offset;
 };
 
 /* struct reg_saved is used to record that a register value has been saved at