diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index 92953001d3..81a52f4744 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -82,6 +82,9 @@ unset GEM_PATH
 # bash processes inside builds
 unset BASH_ENV
 
+# Users may have this set, breaking grep's output.
+unset GREP_OPTIONS
+
 HOMEBREW_SYSTEM="$(uname -s)"
 case "$HOMEBREW_SYSTEM" in
   Darwin) HOMEBREW_MACOS="1" ;;
diff --git a/Library/Homebrew/extend/ENV/shared.rb b/Library/Homebrew/extend/ENV/shared.rb
index a93c1ee1f6..7b468574ad 100644
--- a/Library/Homebrew/extend/ENV/shared.rb
+++ b/Library/Homebrew/extend/ENV/shared.rb
@@ -17,7 +17,7 @@ module SharedEnvExtension
   FC_FLAG_VARS = %w[FCFLAGS FFLAGS].freeze
   # @private
   SANITIZED_VARS = %w[
-    CDPATH GREP_OPTIONS CLICOLOR_FORCE
+    CDPATH CLICOLOR_FORCE
     CPATH C_INCLUDE_PATH CPLUS_INCLUDE_PATH OBJC_INCLUDE_PATH
     CC CXX OBJC OBJCXX CPP MAKE LD LDSHARED
     CFLAGS CXXFLAGS OBJCFLAGS OBJCXXFLAGS LDFLAGS CPPFLAGS