diff --git a/include/fmt/base.h b/include/fmt/base.h
index 783e0368..f440cffd 100644
--- a/include/fmt/base.h
+++ b/include/fmt/base.h
@@ -23,7 +23,7 @@
 #endif
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 110000
+#define FMT_VERSION 110001
 
 // Detect compiler versions.
 #if defined(__clang__) && !defined(__ibmxl__)
@@ -262,7 +262,7 @@
 #ifndef FMT_BEGIN_NAMESPACE
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    inline namespace v10 {
+    inline namespace v11 {
 #  define FMT_END_NAMESPACE \
     }                       \
     }
diff --git a/support/manage.py b/support/manage.py
index ae5252fc..928affe2 100755
--- a/support/manage.py
+++ b/support/manage.py
@@ -144,6 +144,16 @@ def release(args):
     if first_section[0] == '\n':
         first_section.pop(0)
 
+    ns_version = None
+    for line in fileinput.input(os.path.join(fmt_repo.dir, 'base.h')):
+        m = re.match(r'inline namespace v(.*)', line)
+        if m:
+            ns_version = m.group(1)
+            break
+    major_version = version.split('.')[0]
+    if not ns_version or ns_version != major_version:
+        raise Exception(f'Version mismatch {ns_version} != {major_version}')
+
     # Workaround GitHub-flavored Markdown treating newlines as <br>.
     changes = ''
     code_block = False