Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -2360,9 +2360,6 @@
   // Treat blocks as analysis entry points.
   CmdArgs.push_back("-analyzer-opt-analyze-nested-blocks");
 
-  // Enable compatilibily mode to avoid analyzer-config related errors.
-  CmdArgs.push_back("-analyzer-config-compatibility-mode=true");
-
   // Add default argument set.
   if (!Args.hasArg(options::OPT__analyzer_no_default_checks)) {
     CmdArgs.push_back("-analyzer-checker=core");
@@ -3694,6 +3691,18 @@
   if (isa<AnalyzeJobAction>(JA))
     RenderAnalyzerOptions(Args, CmdArgs, Triple, Input);
 
+  // Enable compatilibily mode to avoid analyzer-config related errors.
+  // Since we can't access frontend flags through hasArg, let's manually iterate
+  // through them.
+  for (size_t Index = 0; Index < Args.getNumInputArgStrings(); ++Index) {
+    if (const char *str = Args.getArgString(Index)) {
+      if (StringRef(str).contains("-analyzer-config")) {
+        CmdArgs.push_back("-analyzer-config-compatibility-mode=true");
+        break;
+      }
+    }
+  }
+
   CheckCodeGenerationOptions(D, Args);
 
   unsigned FunctionAlignment = ParseFunctionAlignment(TC, Args);
Index: test/Analysis/invalid-a-na-ly-zer-con-fig-value.c
===================================================================
--- /dev/null
+++ test/Analysis/invalid-a-na-ly-zer-con-fig-value.c
@@ -0,0 +1,80 @@
+// Same as invalid-analyzer-config-value.c but without -analyzer-config
+// in the file name, so that argument string pattern matching
+// didn't accidentally match it.
+
+// RUN: not %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config notes-as-events=yesplease \
+// RUN:   2>&1 | FileCheck %s -check-prefix=CHECK-BOOL-INPUT
+
+// CHECK-BOOL-INPUT: (frontend): invalid input for analyzer-config option
+// CHECK-BOOL-INPUT-SAME:        'notes-as-events', that expects a boolean value
+
+// RUN: %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config-compatibility-mode=true \
+// RUN:   -analyzer-config notes-as-events=yesplease
+
+
+// RUN: not %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config max-inlinable-size=400km/h \
+// RUN:   2>&1 | FileCheck %s -check-prefix=CHECK-UINT-INPUT
+
+// CHECK-UINT-INPUT: (frontend): invalid input for analyzer-config option
+// CHECK-UINT-INPUT-SAME:        'max-inlinable-size', that expects an unsigned
+// CHECK-UINT-INPUT-SAME:        value
+
+// RUN: %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config-compatibility-mode=true \
+// RUN:   -analyzer-config max-inlinable-size=400km/h
+
+
+// RUN: not %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config ctu-dir=0123012301230123 \
+// RUN:   2>&1 | FileCheck %s -check-prefix=CHECK-FILENAME-INPUT
+
+// CHECK-FILENAME-INPUT: (frontend): invalid input for analyzer-config option
+// CHECK-FILENAME-INPUT-SAME:        'ctu-dir', that expects a filename
+// CHECK-FILENAME-INPUT-SAME:        value
+
+// RUN: %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config-compatibility-mode=true \
+// RUN:   -analyzer-config ctu-dir=0123012301230123
+
+
+// RUN: not %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config no-false-positives=true \
+// RUN:   2>&1 | FileCheck %s -check-prefix=CHECK-UNKNOWN-CFG
+
+// CHECK-UNKNOWN-CFG: (frontend): unknown analyzer-config 'no-false-positives'
+
+// RUN: %clang_analyze_cc1 -verify %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-config-compatibility-mode=true \
+// RUN:   -analyzer-config no-false-positives=true
+
+
+// Test the driver properly using "analyzer-config-compatibility-mode=true",
+// no longer causing an error on input error.
+// RUN: %clang --analyze %s
+
+// RUN: not %clang --analyze %s \
+// RUN:   -Xclang -analyzer-config -Xclang no-false-positives=true \
+// RUN:   -Xclang -analyzer-config-compatibility-mode=false \
+// RUN:   2>&1 | FileCheck %s -check-prefix=CHECK-NO-COMPAT
+
+// CHECK-NO-COMPAT: error: unknown analyzer-config 'no-false-positives'
+
+// Test the driver properly using "analyzer-config-compatibility-mode=true",
+// even if -analyze isn't specified.
+// RUN: %clang -fsyntax-only -Xclang -analyzer-config\
+// RUN:                      -Xclang remember=TheVasa %s
+
+// expected-no-diagnostics
+
+int main() {}
Index: test/Analysis/invalid-analyzer-config-value.c
===================================================================
--- test/Analysis/invalid-analyzer-config-value.c
+++ test/Analysis/invalid-analyzer-config-value.c
@@ -66,6 +66,11 @@
 
 // CHECK-NO-COMPAT: error: unknown analyzer-config 'no-false-positives'
 
+// Test the driver properly using "analyzer-config-compatibility-mode=true",
+// even if -analyze isn't specified.
+// RUN: %clang -fsyntax-only -Xclang -analyzer-config\
+// RUN:                      -Xclang remember=TheVasa %s
+
 // expected-no-diagnostics
 
 int main() {}