diff --git a/README.md b/README.md
index b86b318..ad38ccf 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,7 @@ inspectrum supports the following file types:
  * `*.cf32`, `*.cfile` - Complex 32-bit floating point samples (GNURadio, osmocom_fft)
  * `*.cs32` - Complex 8-bit signed integer samples (HackRF)
  * `*.cu32` - Complex 8-bit unsigned integer samples (RTL-SDR)
+If an unknown file extension is loaded, inspectrum will default to `*.cf32`.
 
 ## Features
  * Spectrogram with zoom/pan
diff --git a/inputsource.cpp b/inputsource.cpp
index adda711..af9f49a 100644
--- a/inputsource.cpp
+++ b/inputsource.cpp
@@ -134,7 +134,7 @@ void InputSource::openFile(const char *filename)
         sampleAdapter = std::unique_ptr<SampleAdapter>(new ComplexU8SampleAdapter());
     }
     else {
-        throw std::runtime_error("Invalid file extension");
+        sampleAdapter = std::unique_ptr<SampleAdapter>(new ComplexF32SampleAdapter());
     }
 
     FILE *file = fopen(filename, "rb");