diff --git a/infer/models/objc/src/NSString.h b/infer/models/objc/src/NSString.h
index 290ddb849..fc2fbb1ae 100644
--- a/infer/models/objc/src/NSString.h
+++ b/infer/models/objc/src/NSString.h
@@ -17,5 +17,6 @@
 + (instancetype)localizedStringWithFormat:(NSString*)format, ...;
 - (instancetype)initWithFormat:(NSString*)format, ...;
 - (instancetype)initWithFormat:(NSString*)format arguments:(va_list)argList;
+- (instancetype)stringByAppendingString:(NSString*)aString;
 - (void)dealloc;
 @end
diff --git a/infer/models/objc/src/NSString.m b/infer/models/objc/src/NSString.m
index 3b0b0dcea..a50d67315 100644
--- a/infer/models/objc/src/NSString.m
+++ b/infer/models/objc/src/NSString.m
@@ -82,6 +82,11 @@ typedef NSUInteger NSStringEncoding;
   }
 }
 
+- (instancetype)stringByAppendingString:(NSString*)aString {
+  const char* v = aString->value;
+  return self;
+}
+
 - (void)dealloc {
   if (self != nil && self->value != 0) {
     free((void*)self->value);
diff --git a/infer/tests/codetoanalyze/objc/errors/Makefile b/infer/tests/codetoanalyze/objc/errors/Makefile
index fb8d266ca..c94b72bb6 100644
--- a/infer/tests/codetoanalyze/objc/errors/Makefile
+++ b/infer/tests/codetoanalyze/objc/errors/Makefile
@@ -30,6 +30,7 @@ SOURCES_DEFAULT = \
   npe/ivar_blocks.m \
   npe/skip_method_with_nil_object.m \
   npe/Nsstring_length_no_npe.m \
+  npe/Nsstring_nil_args.m \
   npe/No_null_from_array.m \
   procdescs/MethodCall.m \
   property/main.c \
diff --git a/infer/tests/codetoanalyze/objc/errors/issues.exp b/infer/tests/codetoanalyze/objc/errors/issues.exp
index c6945b603..c83e8a951 100644
--- a/infer/tests/codetoanalyze/objc/errors/issues.exp
+++ b/infer/tests/codetoanalyze/objc/errors/issues.exp
@@ -78,6 +78,10 @@ codetoanalyze/objc/errors/memory_leaks_benchmark/NSString_models_tests.m, String
 codetoanalyze/objc/errors/memory_leaks_benchmark/RetainCycleLength3.m, strongcycle, 6, RETAIN_CYCLE, no_bucket, ERROR, [start of procedure strongcycle(),Executing synthesized setter setB:,Executing synthesized setter setC:,Executing synthesized setter setA:]
 codetoanalyze/objc/errors/npe/Fraction.m, test_virtual_call, 7, NULL_DEREFERENCE, B1, ERROR, [start of procedure test_virtual_call(),start of procedure setNumerator:,return from a call to Fraction_setNumerator:,start of procedure getNumerator,return from a call to Fraction_getNumerator,Taking true branch]
 codetoanalyze/objc/errors/npe/Npe_with_equal_names.m, EqualNamesTest, 3, NULL_DEREFERENCE, B1, ERROR, [start of procedure EqualNamesTest(),start of procedure meth,return from a call to EqualNamesA_meth]
+codetoanalyze/objc/errors/npe/Nsstring_nil_args.m, initWithFormatBad, 3, NULL_DEREFERENCE, B1, ERROR, [start of procedure initWithFormatBad()]
+codetoanalyze/objc/errors/npe/Nsstring_nil_args.m, stringByAppendingStringBad, 2, NULL_DEREFERENCE, B1, ERROR, [start of procedure stringByAppendingStringBad()]
+codetoanalyze/objc/errors/npe/Nsstring_nil_args.m, stringWithStringBad, 2, NULL_DEREFERENCE, B1, ERROR, [start of procedure stringWithStringBad(),start of procedure nullableMethod(),return from a call to nullableMethod]
+codetoanalyze/objc/errors/npe/Nsstring_nil_args.m, stringWithUTF8StringBad, 1, NULL_DEREFERENCE, B5, ERROR, [start of procedure stringWithUTF8StringBad(),start of procedure nullableMethod(),return from a call to nullableMethod]
 codetoanalyze/objc/errors/npe/block.m, BlockA_doSomethingThenCallback:, 2, PARAMETER_NOT_NULL_CHECKED, B1, WARNING, [start of procedure doSomethingThenCallback:]
 codetoanalyze/objc/errors/npe/block.m, BlockA_foo, 5, NULL_DEREFERENCE, B1, ERROR, [start of procedure foo]
 codetoanalyze/objc/errors/npe/block.m, BlockA_foo3:, 3, NULL_DEREFERENCE, B1, ERROR, [start of procedure foo3:]
diff --git a/infer/tests/codetoanalyze/objc/errors/npe/Nsstring_nil_args.m b/infer/tests/codetoanalyze/objc/errors/npe/Nsstring_nil_args.m
new file mode 100644
index 000000000..a2a083406
--- /dev/null
+++ b/infer/tests/codetoanalyze/objc/errors/npe/Nsstring_nil_args.m
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <Foundation/NSString.h>
+
+NSString* nullableMethod() { return nil; }
+
+NSString* stringWithUTF8StringGood() {
+  NSString* str = [NSString stringWithUTF8String:"a"];
+  return str;
+}
+
+NSString* stringWithUTF8StringBad() {
+  NSString* str = [NSString stringWithUTF8String:nullableMethod()];
+  return str;
+}
+
+NSString* stringWithStringGood() {
+  NSString* str = [NSString stringWithString:@"a"];
+  return str;
+}
+
+NSString* stringWithStringBad() {
+  NSString* s = nullableMethod();
+  NSString* str = [NSString stringWithString:s];
+  return str;
+}
+
+NSString* initWithFormatGood() {
+  NSString* str = @"a";
+  [str initWithFormat:@"a"];
+  return str;
+}
+
+NSString* initWithFormatBad() {
+  NSString* str = @"a";
+  NSString* fmt = nil;
+  [str initWithFormat:fmt];
+  return str;
+}
+
+NSString* stringByAppendingStringGood() {
+  NSString* str = @"a";
+  [str stringByAppendingString:@"b"];
+  return str;
+}
+
+NSString* stringByAppendingStringBad() {
+  NSString* str = @"a";
+  [str stringByAppendingString:nil];
+  return str;
+}