diff --git a/src/bigint.cpp b/src/bigint.cpp
index 367ae79b6c79e6bd8fe66fc7c00dee7dca6ad0d6..bb227a7c3d5bb266257cae23c781445419b7f07f 100644
--- a/src/bigint.cpp
+++ b/src/bigint.cpp
@@ -1683,10 +1683,15 @@ void bigint_incr(BigInt *x) {
         bigint_init_unsigned(x, 1);
         return;
     }
-    
-    if (x->digit_count == 1 && x->data.digit != UINT64_MAX) {
-        x->data.digit += 1;
-        return;
+
+    if (x->digit_count == 1) {
+        if (x->is_negative && x->data.digit != 0) {
+            x->data.digit -= 1;
+            return;
+        } else if (!x->is_negative && x->data.digit != UINT64_MAX) {
+            x->data.digit += 1;
+            return;
+        }
     }
 
     BigInt copy;
diff --git a/test/behavior.zig b/test/behavior.zig
index 096c07b2e0261096a8376cd4b6626ee48dc2944d..b494c623e25748d5e32581865b8fb1e760a969f9 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -13,6 +13,7 @@ comptime {
     _ = @import("cases/bugs/656.zig");
     _ = @import("cases/bugs/828.zig");
     _ = @import("cases/bugs/920.zig");
+    _ = @import("cases/bugs/1111.zig");
     _ = @import("cases/byval_arg_var.zig");
     _ = @import("cases/cast.zig");
     _ = @import("cases/const_slice_child.zig");
diff --git a/test/cases/bugs/1111.zig b/test/cases/bugs/1111.zig
new file mode 100644
index 0000000000000000000000000000000000000000..51ce90af52cdfc544cff017c9a3a3153a69f3105
--- /dev/null
+++ b/test/cases/bugs/1111.zig
@@ -0,0 +1,12 @@
+const Foo = extern enum {
+    Bar = -1,
+};
+
+test "issue 1111 fixed" {
+    const v = Foo.Bar;
+
+    switch(v) {
+    Foo.Bar => return,
+    else => return,
+    }
+}