diff --git a/lib/proxy/db.c b/lib/proxy/db.c
index 2a556e0..a0bfe34 100644
--- a/lib/proxy/db.c
+++ b/lib/proxy/db.c
@@ -38,7 +38,8 @@ int proxy_db_exec_stmt(pool *p, const char *stmt, const char **errstr) {
   char *ptr = NULL;
   unsigned int nretries = 0;
 
-  if (stmt == NULL) {
+  if (p == NULL ||
+      stmt == NULL) {
     errno = EINVAL;
     return -1;
   }
@@ -141,7 +142,8 @@ int proxy_db_bind_stmt(pool *p, const char *stmt, int idx, int type,
   sqlite3_stmt *pstmt;
   int res;
  
-  if (stmt == NULL) {
+  if (p == NULL ||
+      stmt == NULL) {
     errno = EINVAL;
     return -1;
   }
@@ -169,6 +171,11 @@ int proxy_db_bind_stmt(pool *p, const char *stmt, int idx, int type,
     case PROXY_DB_BIND_TYPE_INT: {
       int i;
 
+      if (data == NULL) {
+        errno = EINVAL;
+        return -1;
+      }
+
       i = *((int *) data);
       res = sqlite3_bind_int(pstmt, idx, i);
       if (res != SQLITE_OK) {
@@ -182,6 +189,11 @@ int proxy_db_bind_stmt(pool *p, const char *stmt, int idx, int type,
     case PROXY_DB_BIND_TYPE_LONG: {
       long l;
 
+      if (data == NULL) {
+        errno = EINVAL;
+        return -1;
+      }
+
       l = *((long *) data);
       res = sqlite3_bind_int(pstmt, idx, l);
       if (res != SQLITE_OK) {
@@ -195,6 +207,11 @@ int proxy_db_bind_stmt(pool *p, const char *stmt, int idx, int type,
     case PROXY_DB_BIND_TYPE_TEXT: {
       const char *text;
 
+      if (data == NULL) {
+        errno = EINVAL;
+        return -1;
+      }
+
       text = (const char *) data;
       res = sqlite3_bind_text(pstmt, idx, text, -1, NULL);
       if (res != SQLITE_OK) {
@@ -228,7 +245,8 @@ int proxy_db_finish_stmt(pool *p, const char *stmt) {
   sqlite3_stmt *pstmt;
   int res;
 
-  if (stmt == NULL) {
+  if (p == NULL ||
+      stmt == NULL) {
     errno = EINVAL;
     return -1;
   }
@@ -265,7 +283,8 @@ array_header *proxy_db_exec_prepared_stmt(pool *p, const char *stmt,
   int readonly = FALSE, res;
   array_header *results = NULL;
 
-  if (stmt == NULL) {
+  if (p == NULL ||
+      stmt == NULL) {
     errno = EINVAL;
     return NULL;
   }
@@ -441,6 +460,11 @@ int proxy_db_open(pool *p, const char *table_path) {
 }
 
 int proxy_db_close(pool *p) {
+  if (p == NULL) {
+    errno = EINVAL;
+    return -1;
+  }
+
   if (proxy_dbh != NULL) {
     sqlite3_stmt *pstmt;
     int res;
diff --git a/t/api/conn.c b/t/api/conn.c
index 034efff..a0bec62 100644
--- a/t/api/conn.c
+++ b/t/api/conn.c
@@ -143,7 +143,7 @@ START_TEST (conn_get_hostport_test) {
 }
 END_TEST
 
-START_TEST (conn_get_url_test) {
+START_TEST (conn_get_uri_test) {
   struct proxy_conn *pconn;
   const char *pconn_url, *url;
 
@@ -176,7 +176,7 @@ Suite *tests_get_conn_suite(void) {
   tcase_add_test(testcase, conn_create_test);
   tcase_add_test(testcase, conn_get_addr_test);
   tcase_add_test(testcase, conn_get_hostport_test);
-  tcase_add_test(testcase, conn_get_url_test);
+  tcase_add_test(testcase, conn_get_uri_test);
 
   suite_add_tcase(suite, testcase);
   return suite;
diff --git a/t/api/db.c b/t/api/db.c
index 9e78685..22ff2aa 100644
--- a/t/api/db.c
+++ b/t/api/db.c
@@ -58,26 +58,84 @@ START_TEST (db_open_test) {
 END_TEST
 
 START_TEST (db_close_test) {
+  int res;
+
+  res = proxy_db_close(NULL);
+  fail_unless(res == -1, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST
 
 START_TEST (db_prepare_stmt_test) {
+  int res;
+
+  res = proxy_db_prepare_stmt(NULL, NULL);
+  fail_unless(res == -1, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST
 
 START_TEST (db_finish_stmt_test) {
+  int res;
+  const char *stmt;
+
+  res = proxy_db_finish_stmt(NULL, NULL);
+  fail_unless(res == -1, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
+
+  stmt = "SELECT COUNT(*) FROM table";
+  res = proxy_db_finish_stmt(p, stmt);
+  fail_unless(res == -1, "Failed to handle unprepared statement");
+  fail_unless(errno == ENOENT, "Failed to set errno to ENOENT, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST
 
 START_TEST (db_bind_stmt_test) {
+  int res;
+  const char *stmt;
+  int idx, type;
+
+  res = proxy_db_bind_stmt(NULL, NULL, -1, -1, NULL);
+  fail_unless(res == -1, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
+
+  stmt = "SELECT COUNT(*) FROM table";
+  idx = -1;
+  res = proxy_db_bind_stmt(p, stmt, idx, PROXY_DB_BIND_TYPE_INT, NULL);
+  fail_unless(res == -1, "Failed to handle invalid index %d", idx);
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
+
+  idx = 1;
+  res = proxy_db_bind_stmt(p, stmt, idx, PROXY_DB_BIND_TYPE_INT, NULL);
+  fail_unless(res == -1, "Failed to handle unprepared statement");
+  fail_unless(errno == ENOENT, "Failed to set errno to ENOENT, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST
 
 START_TEST (db_exec_stmt_test) {
+  int res;
+
+  res = proxy_db_exec_stmt(NULL, NULL, NULL);
+  fail_unless(res == -1, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST
 
 START_TEST (db_exec_prepared_stmt_test) {
+  array_header *res;
+
+  res = proxy_db_exec_prepared_stmt(NULL, NULL, NULL);
+  fail_unless(res == NULL, "Failed to handle null arguments");
+  fail_unless(errno == EINVAL, "Failed to set errno to EINVAL, got %s (%d)",
+    strerror(errno), errno);
 }
 END_TEST