diff --git a/lib/database.cc b/lib/database.cc
index e4ac970f..414460d2 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -185,7 +185,7 @@ typedef struct {
  * nearly universal to all mail messages).
  */
 
-prefix_t BOOLEAN_PREFIX_INTERNAL[] = {
+static prefix_t BOOLEAN_PREFIX_INTERNAL[] = {
     { "type",			"T" },
     { "reference",		"XREFERENCE" },
     { "replyto",		"XREPLYTO" },
@@ -194,14 +194,14 @@ prefix_t BOOLEAN_PREFIX_INTERNAL[] = {
     { "directory-direntry",	"XDDIRENTRY" },
 };
 
-prefix_t BOOLEAN_PREFIX_EXTERNAL[] = {
+static prefix_t BOOLEAN_PREFIX_EXTERNAL[] = {
     { "thread",			"G" },
     { "tag",			"K" },
     { "is",			"K" },
     { "id",			"Q" }
 };
 
-prefix_t PROBABILISTIC_PREFIX[]= {
+static prefix_t PROBABILISTIC_PREFIX[]= {
     { "from",			"XFROM" },
     { "to",			"XTO" },
     { "attachment",		"XATTACHMENT" },
diff --git a/lib/directory.cc b/lib/directory.cc
index 5d673e21..f576e336 100644
--- a/lib/directory.cc
+++ b/lib/directory.cc
@@ -52,7 +52,7 @@ _notmuch_filenames_destructor (notmuch_filenames_t *filenames)
  * iterating over the non-prefixed portion of terms sharing a common
  * prefix.
  */
-notmuch_filenames_t *
+static notmuch_filenames_t *
 _notmuch_filenames_create (void *ctx,
 			   notmuch_database_t *notmuch,
 			   const char *prefix)
diff --git a/lib/index.cc b/lib/index.cc
index 0d6640bc..00478f8d 100644
--- a/lib/index.cc
+++ b/lib/index.cc
@@ -63,7 +63,7 @@ struct _NotmuchFilterDiscardUuencodeClass {
     GMimeFilterClass parent_class;
 };
 
-GMimeFilter *notmuch_filter_discard_uuencode_new (void);
+static GMimeFilter *notmuch_filter_discard_uuencode_new (void);
 
 static void notmuch_filter_discard_uuencode_finalize (GObject *object);
 
@@ -195,7 +195,7 @@ filter_reset (GMimeFilter *gmime_filter)
  *
  * Returns: a new #NotmuchFilterDiscardUuencode filter.
  **/
-GMimeFilter *
+static GMimeFilter *
 notmuch_filter_discard_uuencode_new (void)
 {
     static GType type = 0;
diff --git a/lib/thread.cc b/lib/thread.cc
index 13872d46..c2914039 100644
--- a/lib/thread.cc
+++ b/lib/thread.cc
@@ -140,14 +140,14 @@ _complete_thread_authors (notmuch_thread_t *thread)
     thread->authors_array = NULL;
 }
 
-/* clean up the uggly "Lastname, Firstname" format that some mail systems
+/* clean up the ugly "Lastname, Firstname" format that some mail systems
  * (most notably, Exchange) are creating to be "Firstname Lastname"
  * To make sure that we don't change other potential situations where a
  * comma is in the name, we check that we match one of these patterns
  * "Last, First" <first.last@company.com>
  * "Last, First MI" <first.mi.last@company.com>
  */
-char *
+static char *
 _thread_cleanup_author (notmuch_thread_t *thread,
 			const char *author, const char *from)
 {