diff --git a/libqpdf/BitStream.cc b/libqpdf/BitStream.cc
index 3b8e7022..d0e991df 100644
--- a/libqpdf/BitStream.cc
+++ b/libqpdf/BitStream.cc
@@ -2,9 +2,9 @@
 
 #include <qpdf/QIntC.hh>
 
-// See comments in bits_include.cc
+// See comments in bits_functions.hh
 #define BITS_READ 1
-#include "bits_include.cc"
+#include <qpdf/bits_functions.hh>
 
 BitStream::BitStream(unsigned char const* p, size_t nbytes) :
     start(p),
diff --git a/libqpdf/BitWriter.cc b/libqpdf/BitWriter.cc
index 81c47db8..9d324734 100644
--- a/libqpdf/BitWriter.cc
+++ b/libqpdf/BitWriter.cc
@@ -1,8 +1,8 @@
 #include <qpdf/BitWriter.hh>
 
-// See comments in bits_include.cc
+// See comments in bits_functions.hh
 #define BITS_WRITE 1
-#include "bits_include.cc"
+#include <qpdf/bits_functions.hh>
 
 BitWriter::BitWriter(Pipeline* pl) :
     pl(pl),
diff --git a/libqpdf/bits_include.cc b/libqpdf/qpdf/bits_functions.hh
similarity index 86%
rename from libqpdf/bits_include.cc
rename to libqpdf/qpdf/bits_functions.hh
index 0f52b4e7..c00a0bcb 100644
--- a/libqpdf/bits_include.cc
+++ b/libqpdf/qpdf/bits_functions.hh
@@ -1,7 +1,5 @@
-// This file is #included in other source files.
-
-#ifndef __BITS_CC__
-#define __BITS_CC__
+#ifndef __BITS_FUNCTIONS_HH__
+#define __BITS_FUNCTIONS_HH__
 
 #include <algorithm>
 #include <stdexcept>
@@ -9,12 +7,13 @@
 #include <qpdf/Pipeline.hh>
 #include <qpdf/QUtil.hh>
 
-// These functions may be run at places where the function call
-// overhead from test coverage testing would be too high.  Therefore,
-// we make the test coverage cases conditional upon a preprocessor
-// symbol.  BitStream.cc includes this file without defining the
-// symbol, and the specially designed test code that fully exercises
-// this code includes with the symbol defined.
+// This file is #included by specific source files, which must define
+// certain preprocessor symbols. These functions may be run at places
+// where the function call overhead from test coverage testing would
+// be too high. Therefore, we make the test coverage cases conditional
+// upon a preprocessor symbol. Library code includes this file without
+// BITS_TESTING, and the specially designed test code that fully
+// exercises this code includes with the symbol defined.
 
 #ifdef BITS_READ
 static unsigned long long
@@ -151,5 +150,4 @@ write_bits(unsigned char& ch, size_t& bit_offset,
 }
 #endif
 
-
-#endif // __BITS_CC__
+#endif // __BITS_FUNCTIONS_HH__
diff --git a/libtests/bits.cc b/libtests/bits.cc
index 81b44566..2c3dc349 100644
--- a/libtests/bits.cc
+++ b/libtests/bits.cc
@@ -7,11 +7,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-// See comments in bits_include.cc
+// See comments in bits_functions.hh
 #define BITS_TESTING 1
 #define BITS_READ 1
 #define BITS_WRITE 1
-#include "../libqpdf/bits_include.cc"
+#include <qpdf/bits_functions.hh>
 
 static void
 print_values(long long byte_offset, size_t bit_offset,
diff --git a/libtests/build.mk b/libtests/build.mk
index 0b9f6fae..6d3371f1 100644
--- a/libtests/build.mk
+++ b/libtests/build.mk
@@ -38,7 +38,7 @@ $(TARGETS_libtests): $(TARGETS_libqpdf) $(TARGETS_qpdf)
 
 INCLUDES_libtests = include libqpdf
 
-TC_SRCS_libtests = $(wildcard libqpdf/*.cc) $(wildcard libtests/*.cc)
+TC_SRCS_libtests = $(wildcard libqpdf/*.cc) $(wildcard libtests/*.cc) libqpdf/qpdf/bits_functions.hh
 
 # -----