diff --git a/setupext.py b/setupext.py
index 19c2868bda32..b63b2908a468 100644
--- a/setupext.py
+++ b/setupext.py
@@ -652,6 +652,7 @@ def get_extensions(self):
             'src/_macosx.m'
             ]
         ext = Extension('matplotlib.backends._macosx', sources)
+        ext.extra_compile_args.extend(['-Werror=unguarded-availability'])
         ext.extra_link_args.extend(['-framework', 'Cocoa'])
         if platform.python_implementation().lower() == 'pypy':
             ext.extra_compile_args.append('-DPYPY=1')
diff --git a/src/_macosx.m b/src/_macosx.m
index 5ce5d203ea67..0bb9057cf5f6 100755
--- a/src/_macosx.m
+++ b/src/_macosx.m
@@ -1207,8 +1207,10 @@ -(void)save_figure:(id)sender
     rect.size.height = 0;
     rect.origin.x += height;
     NSTextView* messagebox = [[NSTextView alloc] initWithFrame: rect];
-    messagebox.textContainer.maximumNumberOfLines = 2;
-    messagebox.textContainer.lineBreakMode = NSLineBreakByTruncatingTail;
+    if (@available(macOS 10.11, *)) {
+        messagebox.textContainer.maximumNumberOfLines = 2;
+        messagebox.textContainer.lineBreakMode = NSLineBreakByTruncatingTail;
+    }
     [messagebox setFont: font];
     [messagebox setDrawsBackground: NO];
     [messagebox setSelectable: NO];