diff --git a/command-line-arguments.c b/command-line-arguments.c
index a4a8bb4c..d64aa85b 100644
--- a/command-line-arguments.c
+++ b/command-line-arguments.c
@@ -4,13 +4,19 @@
 #include "error_util.h"
 #include "command-line-arguments.h"
 
+typedef enum {
+    OPT_FAILED, /* false */
+    OPT_OK, /* good */
+    OPT_GIVEBACK, /* pop one of the arguments you thought you were getting off the stack */
+} opt_handled;
+
 /*
   Search the array of keywords for a given argument, assigning the
   output variable to the corresponding value.  Return false if nothing
   matches.
 */
 
-static bool
+static opt_handled
 _process_keyword_arg (const notmuch_opt_desc_t *arg_desc, char next,
 		      const char *arg_str, bool negate)
 {
@@ -32,16 +38,32 @@ _process_keyword_arg (const notmuch_opt_desc_t *arg_desc, char next,
 	else
 	    *arg_desc->opt_keyword = keywords->value;
 
-	return true;
+	return OPT_OK;
     }
+
+    if (arg_desc->opt_keyword && arg_desc->keyword_no_arg_value && next != ':' && next != '=') {
+	for (keywords = arg_desc->keywords; keywords->name; keywords++) {
+	    if (strcmp (arg_desc->keyword_no_arg_value, keywords->name) != 0)
+		continue;
+
+	    *arg_desc->opt_keyword = keywords->value;
+	    fprintf (stderr, "Warning: No known keyword option given for \"%s\", choosing value \"%s\"."
+		     "  Please specify the argument explicitly!\n", arg_desc->name, arg_desc->keyword_no_arg_value);
+
+	    return OPT_GIVEBACK;
+	}
+	fprintf (stderr, "No matching keyword for option \"%s\" and default value \"%s\" is invalid.\n", arg_str, arg_desc->name);
+	return OPT_FAILED;
+    }
+
     if (next != '\0')
 	fprintf (stderr, "Unknown keyword argument \"%s\" for option \"%s\".\n", arg_str, arg_desc->name);
     else
 	fprintf (stderr, "Option \"%s\" needs a keyword argument.\n", arg_desc->name);
-    return false;
+    return OPT_FAILED;
 }
 
-static bool
+static opt_handled
 _process_boolean_arg (const notmuch_opt_desc_t *arg_desc, char next,
 		      const char *arg_str, bool negate)
 {
@@ -53,45 +75,45 @@ _process_boolean_arg (const notmuch_opt_desc_t *arg_desc, char next,
 	value = false;
     } else {
 	fprintf (stderr, "Unknown argument \"%s\" for (boolean) option \"%s\".\n", arg_str, arg_desc->name);
-	return false;
+	return OPT_FAILED;
     }
 
     *arg_desc->opt_bool = negate ? !value : value;
 
-    return true;
+    return OPT_OK;
 }
 
-static bool
+static opt_handled
 _process_int_arg (const notmuch_opt_desc_t *arg_desc, char next, const char *arg_str) {
 
     char *endptr;
     if (next == '\0' || arg_str[0] == '\0') {
 	fprintf (stderr, "Option \"%s\" needs an integer argument.\n", arg_desc->name);
-	return false;
+	return OPT_FAILED;
     }
 
     *arg_desc->opt_int = strtol (arg_str, &endptr, 10);
     if (*endptr == '\0')
-	return true;
+	return OPT_OK;
 
     fprintf (stderr, "Unable to parse argument \"%s\" for option \"%s\" as an integer.\n",
 	     arg_str, arg_desc->name);
-    return false;
+    return OPT_FAILED;
 }
 
-static bool
+static opt_handled
 _process_string_arg (const notmuch_opt_desc_t *arg_desc, char next, const char *arg_str) {
 
     if (next == '\0') {
 	fprintf (stderr, "Option \"%s\" needs a string argument.\n", arg_desc->name);
-	return false;
+	return OPT_FAILED;
     }
     if (arg_str[0] == '\0' && ! arg_desc->allow_empty) {
 	fprintf (stderr, "String argument for option \"%s\" must be non-empty.\n", arg_desc->name);
-	return false;
+	return OPT_FAILED;
     }
     *arg_desc->opt_string = arg_str;
-    return true;
+    return OPT_OK;
 }
 
 /* Return number of non-NULL opt_* fields in opt_desc. */
@@ -212,13 +234,15 @@ parse_option (int argc, char **argv, const notmuch_opt_desc_t *options, int opt_
 	if (next != '=' && next != ':' && next != '\0')
 	    continue;
 
-	if (next == '\0' && next_arg != NULL && ! try->opt_bool) {
+	bool lookahead = (next == '\0' && next_arg != NULL && ! try->opt_bool);
+
+	if (lookahead) {
 	    next = ' ';
 	    value = next_arg;
 	    opt_index ++;
 	}
 
-	bool opt_status = false;
+	opt_handled opt_status = OPT_FAILED;
 	if (try->opt_keyword || try->opt_flags)
 	    opt_status = _process_keyword_arg (try, next, value, negate);
 	else if (try->opt_bool)
@@ -230,9 +254,12 @@ parse_option (int argc, char **argv, const notmuch_opt_desc_t *options, int opt_
 	else
 	    INTERNAL_ERROR ("unknown or unhandled option \"%s\"", try->name);
 
-	if (! opt_status)
+	if (opt_status == OPT_FAILED)
 	    return -1;
 
+	if (lookahead && opt_status == OPT_GIVEBACK)
+	    opt_index --;
+
 	if (try->present)
 	    *try->present = true;
 
diff --git a/command-line-arguments.h b/command-line-arguments.h
index c0228f7c..f722f97d 100644
--- a/command-line-arguments.h
+++ b/command-line-arguments.h
@@ -26,6 +26,10 @@ typedef struct notmuch_opt_desc {
     const char **opt_string;
     const char **opt_position;
 
+    /* for opt_keyword only: if no matching arguments were found, and
+     * keyword_no_arg_value is set, then use keyword_no_arg_value instead. */
+    const char *keyword_no_arg_value;
+
     /* Must be set except for opt_inherit and opt_position. */
     const char *name;
 
diff --git a/test/T410-argument-parsing.sh b/test/T410-argument-parsing.sh
index 192133c5..a384ce86 100755
--- a/test/T410-argument-parsing.sh
+++ b/test/T410-argument-parsing.sh
@@ -65,4 +65,36 @@ flags 1
 EOF
 test_expect_equal_file EXPECTED OUTPUT
 
+test_begin_subtest "test keyword arguments without value"
+$TEST_DIRECTORY/arg-test --boolkeyword bananas > OUTPUT
+cat <<EOF > EXPECTED
+boolkeyword 1
+positional arg 1 bananas
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "test keyword arguments with non-default value separted by a space"
+$TEST_DIRECTORY/arg-test --boolkeyword false bananas > OUTPUT
+cat <<EOF > EXPECTED
+boolkeyword 0
+positional arg 1 bananas
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "test keyword arguments without value at the end"
+$TEST_DIRECTORY/arg-test bananas --boolkeyword > OUTPUT
+cat <<EOF > EXPECTED
+boolkeyword 1
+positional arg 1 bananas
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "test keyword arguments without value but with = (should be an error)"
+$TEST_DIRECTORY/arg-test bananas --boolkeyword= > OUTPUT 2>&1
+cat <<EOF > EXPECTED
+Unknown keyword argument "" for option "boolkeyword".
+Unrecognized option: --boolkeyword=
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
 test_done
diff --git a/test/arg-test.c b/test/arg-test.c
index 7aff8255..a218f967 100644
--- a/test/arg-test.c
+++ b/test/arg-test.c
@@ -7,13 +7,14 @@ int main(int argc, char **argv){
     int opt_index=1;
 
     int kw_val=0;
+    int kwb_val=0;
     int fl_val=0;
     int int_val=0;
     const char *pos_arg1=NULL;
     const char *pos_arg2=NULL;
     const char *string_val=NULL;
     bool bool_val = false;
-    bool fl_set = false, int_set = false, bool_set = false,
+    bool fl_set = false, int_set = false, bool_set = false, kwb_set = false,
 	kw_set = false, string_set = false, pos1_set = false, pos2_set = false;
 
     notmuch_opt_desc_t parent_options[] = {
@@ -33,6 +34,12 @@ int main(int argc, char **argv){
 				  { "one", 1 },
 				  { "two", 2 },
 				  { 0, 0 } } },
+	{ .opt_keyword = &kwb_val, .name = "boolkeyword", .present = &kwb_set,
+	  .keyword_no_arg_value = "true", .keywords =
+	  (notmuch_keyword_t []){ { "false", 0 },
+				  { "true", 1 },
+				  { "auto", 2 },
+				  { 0, 0 } } },
 	{ .opt_inherit = parent_options },
 	{ .opt_string = &string_val, .name = "string", .present = &string_set },
 	{ .opt_position = &pos_arg1, .present = &pos1_set },
@@ -51,6 +58,9 @@ int main(int argc, char **argv){
     if (kw_set)
 	printf("keyword %d\n", kw_val);
 
+    if (kwb_set)
+	printf("boolkeyword %d\n", kwb_val);
+
     if (fl_set)
 	printf("flags %d\n", fl_val);