diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1899,7 +1899,7 @@
     CIncludeDirs.split(dirs, ":");
     for (llvm::StringRef dir : dirs) {
       llvm::StringRef Prefix =
-          llvm::sys::path::is_absolute(dir) ? llvm::StringRef(Sysroot) : "";
+          llvm::sys::path::is_absolute(dir) ? "" : llvm::StringRef(Sysroot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
     }
   } else {
diff --git a/clang/lib/Driver/ToolChains/Fuchsia.cpp b/clang/lib/Driver/ToolChains/Fuchsia.cpp
--- a/clang/lib/Driver/ToolChains/Fuchsia.cpp
+++ b/clang/lib/Driver/ToolChains/Fuchsia.cpp
@@ -289,7 +289,7 @@
     CIncludeDirs.split(dirs, ":");
     for (StringRef dir : dirs) {
       StringRef Prefix =
-          llvm::sys::path::is_absolute(dir) ? StringRef(D.SysRoot) : "";
+          llvm::sys::path::is_absolute(dir) ? "" : StringRef(D.SysRoot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
     }
     return;
diff --git a/clang/lib/Driver/ToolChains/Hurd.cpp b/clang/lib/Driver/ToolChains/Hurd.cpp
--- a/clang/lib/Driver/ToolChains/Hurd.cpp
+++ b/clang/lib/Driver/ToolChains/Hurd.cpp
@@ -149,7 +149,7 @@
     CIncludeDirs.split(Dirs, ":");
     for (StringRef Dir : Dirs) {
       StringRef Prefix =
-          llvm::sys::path::is_absolute(Dir) ? StringRef(SysRoot) : "";
+          llvm::sys::path::is_absolute(Dir) ? "" : StringRef(SysRoot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + Dir);
     }
     return;
diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -676,7 +676,7 @@
     CIncludeDirs.split(dirs, ":");
     for (StringRef dir : dirs) {
       StringRef Prefix =
-          llvm::sys::path::is_absolute(dir) ? StringRef(SysRoot) : "";
+          llvm::sys::path::is_absolute(dir) ? "" : StringRef(SysRoot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
     }
     return;
diff --git a/clang/lib/Driver/ToolChains/Solaris.cpp b/clang/lib/Driver/ToolChains/Solaris.cpp
--- a/clang/lib/Driver/ToolChains/Solaris.cpp
+++ b/clang/lib/Driver/ToolChains/Solaris.cpp
@@ -244,7 +244,7 @@
     CIncludeDirs.split(dirs, ":");
     for (StringRef dir : dirs) {
       StringRef Prefix =
-          llvm::sys::path::is_absolute(dir) ? StringRef(D.SysRoot) : "";
+          llvm::sys::path::is_absolute(dir) ? "" : StringRef(D.SysRoot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
     }
     return;
diff --git a/clang/lib/Driver/ToolChains/WebAssembly.cpp b/clang/lib/Driver/ToolChains/WebAssembly.cpp
--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -283,7 +283,7 @@
     CIncludeDirs.split(dirs, ":");
     for (StringRef dir : dirs) {
       StringRef Prefix =
-          llvm::sys::path::is_absolute(dir) ? StringRef(D.SysRoot) : "";
+          llvm::sys::path::is_absolute(dir) ? "" : StringRef(D.SysRoot);
       addExternCSystemInclude(DriverArgs, CC1Args, Prefix + dir);
     }
     return;