diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -1674,22 +1674,6 @@
                                               RetType{IntTy}, NoEvalCall)
                                           .ArgConstraint(NotNull(ArgNo(0))));
 
-    // int strcasecmp(const char *s1, const char *s2);
-    addToFunctionSummaryMap("strcasecmp",
-                            Summary(ArgTypes{ConstCharPtrTy, ConstCharPtrTy},
-                                    RetType{IntTy}, EvalCallAsPure)
-                                .ArgConstraint(NotNull(ArgNo(0)))
-                                .ArgConstraint(NotNull(ArgNo(1))));
-
-    // int strncasecmp(const char *s1, const char *s2, size_t n);
-    addToFunctionSummaryMap(
-        "strncasecmp", Summary(ArgTypes{ConstCharPtrTy, ConstCharPtrTy, SizeTy},
-                               RetType{IntTy}, EvalCallAsPure)
-                           .ArgConstraint(NotNull(ArgNo(0)))
-                           .ArgConstraint(NotNull(ArgNo(1)))
-                           .ArgConstraint(ArgumentCondition(
-                               2, WithinRange, Range(0, SizeMax))));
-
     // int fileno(FILE *stream);
     addToFunctionSummaryMap(
         "fileno", Summary(ArgTypes{FilePtrTy}, RetType{IntTy}, NoEvalCall)
diff --git a/clang/test/Analysis/std-c-library-functions-arg-cstring-dependency.c b/clang/test/Analysis/std-c-library-functions-arg-cstring-dependency.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Analysis/std-c-library-functions-arg-cstring-dependency.c
@@ -0,0 +1,21 @@
+// This test case crashes if strncasecmp is modeled in StdCLibraryFunctions.
+// Either we fix CStringChecker to handle the call prerequisites in
+// checkPreCall, or we must not evaluate any pure functions in
+// StdCLibraryFunctions that are also handled in CStringChecker.
+
+// RUN: %clang_analyze_cc1 %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-checker=apiModeling.StdCLibraryFunctions \
+// RUN:   -analyzer-checker=unix.cstring.NullArg \
+// RUN:   -analyzer-config apiModeling.StdCLibraryFunctions:ModelPOSIX=true \
+// RUN:   -analyzer-checker=alpha.unix.StdCLibraryFunctionArgs \
+// RUN:   -triple x86_64-unknown-linux-gnu \
+// RUN:   -verify
+
+typedef __typeof(sizeof(int)) size_t;
+int strncasecmp(const char *s1, const char *s2, size_t n);
+
+int strncasecmp_null_argument(char *a, size_t n) {
+  char *b = 0;
+  return strncasecmp(a, b, n); // expected-warning{{Null pointer passed as 2nd argument to string comparison function}}
+}