diff --git a/lib/filterx/Makefile.am b/lib/filterx/Makefile.am
index 8b495f5051..69b2172795 100644
--- a/lib/filterx/Makefile.am
+++ b/lib/filterx/Makefile.am
@@ -12,6 +12,7 @@ filterxinclude_HEADERS = 			\
 	lib/filterx/expr-setattr.h		\
 	lib/filterx/expr-get-subscript.h	\
 	lib/filterx/expr-set-subscript.h	\
+	lib/filterx/expr-plus.h	\
 	lib/filterx/expr-variable.h		\
 	lib/filterx/expr-comparison.h		\
 	lib/filterx/filterx-object.h		\
@@ -54,6 +55,7 @@ filterx_sources = 				\
 	lib/filterx/expr-setattr.c		\
 	lib/filterx/expr-get-subscript.c	\
 	lib/filterx/expr-set-subscript.c	\
+	lib/filterx/expr-plus.c	\
 	lib/filterx/expr-variable.c		\
 	lib/filterx/expr-comparison.c		\
 	lib/filterx/filterx-object.c		\
diff --git a/lib/filterx/expr-plus.c b/lib/filterx/expr-plus.c
new file mode 100644
index 0000000000..dfcab844b7
--- /dev/null
+++ b/lib/filterx/expr-plus.c
@@ -0,0 +1,56 @@
+#include "expr-plus.h"
+#include "object-string.h"
+#include "filterx-eval.h"
+#include "scratch-buffers.h"
+
+typedef struct FilterXOperatorPlus
+{
+  FilterXBinaryOp super;
+} FilterXOperatorPlus;
+
+static FilterXObject *
+_eval(FilterXExpr *s)
+{
+  FilterXOperatorPlus *self = (FilterXOperatorPlus *) s;
+
+  FilterXObject *lhs_object = filterx_expr_eval(self->super.lhs);
+  if (!lhs_object)
+    {
+      return NULL;
+    }
+
+  FilterXObject *rhs_object = filterx_expr_eval(self->super.rhs);
+  if (!rhs_object)
+    {
+      filterx_object_unref(lhs_object);
+      return NULL;
+    }
+
+  if (filterx_object_is_type(lhs_object, &FILTERX_TYPE_NAME(string)) &&
+      filterx_object_is_type(rhs_object, &FILTERX_TYPE_NAME(string)))
+    {
+      gsize lhs_len, rhs_len;
+      const gchar *lhs_value = filterx_string_get_value(lhs_object, &lhs_len);
+      const gchar *rhs_value = filterx_string_get_value(rhs_object, &rhs_len);
+      GString *buffer = scratch_buffers_alloc();
+
+      g_string_append_len(buffer, lhs_value, lhs_len);
+      g_string_append_len(buffer, rhs_value, rhs_len);
+      /* FIXME: support taking over the already allocated space */
+      return filterx_string_new(buffer->str, buffer->len);
+    }
+
+  filterx_eval_push_error("operator+ only works on strings", s, NULL);
+  filterx_object_unref(lhs_object);
+  filterx_object_unref(rhs_object);
+  return NULL;
+}
+
+FilterXExpr *
+filterx_operator_plus_new(FilterXExpr *lhs, FilterXExpr *rhs)
+{
+  FilterXOperatorPlus *self = g_new0(FilterXOperatorPlus, 1);
+  filterx_binary_op_init_instance(&self->super, lhs, rhs);
+  self->super.super.eval = _eval;
+  return &self->super.super;
+}
diff --git a/lib/filterx/expr-plus.h b/lib/filterx/expr-plus.h
new file mode 100644
index 0000000000..acb51c4a99
--- /dev/null
+++ b/lib/filterx/expr-plus.h
@@ -0,0 +1,8 @@
+#ifndef FILTERX_EXPR_PLUS_H_INCLUDED
+#define FILTERX_EXPR_PLUS_H_INCLUDED
+
+#include "filterx-expr.h"
+
+FilterXExpr *filterx_operator_plus_new(FilterXExpr *lhs, FilterXExpr *rhs);
+
+#endif
diff --git a/lib/filterx/filterx-grammar.ym b/lib/filterx/filterx-grammar.ym
index d0f6bf136a..0d41f392f6 100644
--- a/lib/filterx/filterx-grammar.ym
+++ b/lib/filterx/filterx-grammar.ym
@@ -52,6 +52,7 @@
 #include "filterx/expr-literal-generator.h"
 #include "filterx/expr-shorthand.h"
 #include "filterx/expr-regexp.h"
+#include "filterx/expr-plus.h"
 
 #include "template/templates.h"
 
@@ -299,6 +300,7 @@ expr
         | expr KW_STR_GT expr			{ $$ = filterx_comparison_new($1, $3, FCMPX_STRING_BASED | FCMPX_GT); }
         | expr KW_TAV_EQ expr			{ $$ = filterx_comparison_new($1, $3, FCMPX_TYPE_AND_VALUE_BASED | FCMPX_EQ); }
         | expr KW_TAV_NE expr			{ $$ = filterx_comparison_new($1, $3, FCMPX_TYPE_AND_VALUE_BASED | FCMPX_NE ); }
+	| expr '+' expr				{ $$ = filterx_operator_plus_new($1, $3); }
 	| '(' expr ')'				{ $$ = $2; }
 	| ternary				{ $$ = $1; }
 	| KW_ISSET '(' expr ')'			{ $$ = filterx_isset_new($3); }