diff --git a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
--- a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
@@ -797,7 +797,7 @@
   if (Flags.verbosity)
     Printf("INFO: Seed: %u\n", Seed);
 
-  if (Flags.collect_data_flow && !Flags.fork &&
+  if (Flags.collect_data_flow && Flags.data_flow_trace && !Flags.fork &&
       !(Flags.merge || Flags.set_cover_merge)) {
     if (RunIndividualFiles)
       return CollectDataFlow(Flags.collect_data_flow, Flags.data_flow_trace,
diff --git a/compiler-rt/test/fuzzer/dataflow.test b/compiler-rt/test/fuzzer/dataflow.test
--- a/compiler-rt/test/fuzzer/dataflow.test
+++ b/compiler-rt/test/fuzzer/dataflow.test
@@ -97,6 +97,11 @@
 L20_FUZZM-NEXT: F2 00000000000000000001{{$}}
 L20_FUZZM-NOT: F
 
+# Don't crash with missing data_flow args.
+RUN: rm -rf %t-DFT
+RUN: %t-ThreeFunctionsTest -collect_data_flow=%t-ThreeFunctionsTestDF
+RUN: %t-ThreeFunctionsTest -data_flow_trace=%t-DFT %t/IN/FUZZMU
+
 # Test libFuzzer's built in DFT collection.
 RUN: rm -rf %t-DFT
 RUN: %t-ThreeFunctionsTest  -collect_data_flow=%t-ThreeFunctionsTestDF -data_flow_trace=%t-DFT %t/IN/FUZZMU