diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index ad8057a358..48abb74447 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1335,6 +1335,10 @@ class Formula
     # CMake cache entries for other weak symbols may be added here as needed.
     args << "-DHAVE_CLOCK_GETTIME:INTERNAL=0" if MacOS.version == "10.11" && MacOS::Xcode.version >= "8.0"
 
+    # Ensure CMake is using the same SDK we are using.
+    sdk = MacOS.sdk_path_if_needed
+    args << "-DCMAKE_OSX_SYSROOT=#{sdk}" if sdk
+
     args
   end