diff --git a/CMakeLists.txt b/CMakeLists.txt
index f91b164ab..f0c2149d3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -266,10 +266,14 @@ set (wsjtx_CXXSRCS
   )
 
 set (wsjt_CXXSRCS
-  lib/crc.cpp
+  lib/crc10.cpp
+  lib/crc12.cpp
   )
 # deal with a GCC v6 UB error message
-set_source_files_properties (lib/crc.cpp PROPERTIES COMPILE_FLAGS -fpermissive)
+set_source_files_properties (
+  lib/crc10.cpp
+  lib/crc12.cpp
+  PROPERTIES COMPILE_FLAGS -fpermissive)
 
 if (WIN32)
   set (wsjt_CXXSRCS
@@ -1087,13 +1091,13 @@ target_link_libraries (jt65 wsjt_fort wsjt_cxx)
 add_executable (ldpcsim40 lib/ldpcsim40.f90 wsjtx.rc)
 target_link_libraries (ldpcsim40 wsjt_fort wsjt_cxx)
 
-add_executable (ldpcsim120 lib/fsk4hf/ldpcsim120.f90 lib/crc.cpp wsjtx.rc)
+add_executable (ldpcsim120 lib/fsk4hf/ldpcsim120.f90 wsjtx.rc)
 target_link_libraries (ldpcsim120 wsjt_fort wsjt_cxx)
 
 add_executable (ldpcsim144 lib/ldpcsim144.f90 wsjtx.rc)
 target_link_libraries (ldpcsim144 wsjt_fort wsjt_cxx)
 
-add_executable (ldpcsim168 lib/fsk4hf/ldpcsim168.f90 lib/crc.cpp wsjtx.rc)
+add_executable (ldpcsim168 lib/fsk4hf/ldpcsim168.f90 wsjtx.rc)
 target_link_libraries (ldpcsim168 wsjt_fort wsjt_cxx)
 
 add_executable (msk144sim lib/msk144sim.f90 wsjtx.rc)
diff --git a/lib/crc.cpp b/lib/crc.cpp
deleted file mode 100644
index c4dd12b90..000000000
--- a/lib/crc.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-#include <boost/crc.hpp>
-#include <boost/cstdint.hpp>
-
-extern "C"
-{
-   short crc12 (unsigned char const * data, int length);
-   bool crc12_check (unsigned char const * data, int length);
-   short crc10 (unsigned char const * data, int length);
-   bool crc10_check (unsigned char const * data, int length);
-}
-
-// assumes CRC is last 16 bits of the data and is set to zero
-// caller should assign the returned CRC into the message in big endian byte order
-short crc12 (unsigned char const * data, int length)
-{
-    return boost::augmented_crc<12, 0xc06> (data, length);
-}
-
-bool crc12_check (unsigned char const * data, int length)
-{
-   return !boost::augmented_crc<12, 0xc06> (data, length);
-}
-
-short crc10 (unsigned char const * data, int length)
-{
-    return boost::augmented_crc<10, 0x08f> (data, length);
-}
-
-bool crc10_check (unsigned char const * data, int length)
-{
-   return !boost::augmented_crc<10, 0x08f> (data, length);
-}
diff --git a/lib/crc10.cpp b/lib/crc10.cpp
new file mode 100644
index 000000000..9ebf42ed7
--- /dev/null
+++ b/lib/crc10.cpp
@@ -0,0 +1,24 @@
+#include <boost/crc.hpp>
+
+extern "C"
+{
+   short crc10 (unsigned char const * data, int length);
+   bool crc10_check (unsigned char const * data, int length);
+}
+
+namespace
+{
+  unsigned long constexpr truncated_polynomial = 0x08f;
+}
+
+// assumes CRC is last 16 bits of the data and is set to zero
+// caller should assign the returned CRC into the message in big endian byte order
+short crc10 (unsigned char const * data, int length)
+{
+    return boost::augmented_crc<10, truncated_polynomial> (data, length);
+}
+
+bool crc10_check (unsigned char const * data, int length)
+{
+   return !boost::augmented_crc<10, truncated_polynomial> (data, length);
+}
diff --git a/lib/crc12.cpp b/lib/crc12.cpp
new file mode 100644
index 000000000..e7d0a80ee
--- /dev/null
+++ b/lib/crc12.cpp
@@ -0,0 +1,24 @@
+#include <boost/crc.hpp>
+
+extern "C"
+{
+   short crc12 (unsigned char const * data, int length);
+   bool crc12_check (unsigned char const * data, int length);
+}
+
+namespace
+{
+  unsigned long constexpr truncated_polynomial = 0xc06;
+}
+
+// assumes CRC is last 16 bits of the data and is set to zero
+// caller should assign the returned CRC into the message in big endian byte order
+short crc12 (unsigned char const * data, int length)
+{
+    return boost::augmented_crc<12, truncated_polynomial> (data, length);
+}
+
+bool crc12_check (unsigned char const * data, int length)
+{
+   return !boost::augmented_crc<12, truncated_polynomial> (data, length);
+}