diff --git a/src/runtime/c/pgf/parser.c b/src/runtime/c/pgf/parser.c
index e69ff173e..6f02ed730 100644
--- a/src/runtime/c/pgf/parser.c
+++ b/src/runtime/c/pgf/parser.c
@@ -55,6 +55,7 @@ typedef struct {
     int prod_full_count;
 #endif
     PgfItem* free_item;
+    prob_t beam_size;
 } PgfParsing;
 
 typedef struct {
@@ -75,6 +76,7 @@ GU_DEFINE_TYPE(PgfProductionIdx, GuMap,
 typedef struct {
 	PgfToken tok;
     PgfProductionIdx* lexicon_idx;
+    prob_t lexical_prob;
 } PgfTokenState;
 
 struct PgfParseState {
@@ -1483,8 +1485,12 @@ pgf_parsing_proceed(PgfParseState* state) {
 			}
 		}
 
-		delta_prob += 
-			(st->viterbi_prob-(st->next ? st->next->viterbi_prob : 0))*0.95;
+		prob_t state_delta =
+			(st->viterbi_prob-(st->next ? st->next->viterbi_prob : 0))*
+			state->ps->beam_size;
+		prob_t lexical_prob =
+			st->ts ? st->ts->lexical_prob : 0;
+		delta_prob += fmax(state_delta, lexical_prob);
 		st = st->next;
 	}
 
@@ -1532,6 +1538,7 @@ pgf_new_parsing(PgfConcr* concr, GuPool* pool)
 	ps->prod_full_count = 0;
 #endif
 	ps->free_item = NULL;
+	ps->beam_size = 0.95;
 
 	PgfExprMeta *expr_meta =
 		gu_new_variant(PGF_EXPR_META,
@@ -1569,6 +1576,38 @@ pgf_new_parse_state(PgfParsing* ps,
 	return state;
 }
 
+typedef struct {
+	GuMapItor fn;
+	PgfTokenState* ts;
+} PgfLexiconFn;
+
+static void
+pgf_parser_compute_lexicon_prob(GuMapItor* fn, const void* key, void* value, GuExn* err)
+{
+	PgfTokenState* ts = ((PgfLexiconFn*) fn)->ts;
+	PgfProductionSeq prods = *((PgfProductionSeq*) value);
+	
+	if (gu_seq_is_null(prods))
+		return;
+	
+	size_t n_prods = gu_seq_length(prods);
+	for (size_t i = 0; i < n_prods; i++) {
+		PgfProduction prod =
+			gu_seq_get(prods, PgfProduction, i);
+
+		GuVariantInfo pi = gu_variant_open(prod);
+		switch (pi.tag) {
+		case PGF_PRODUCTION_APPLY: {
+			PgfProductionApply* papp = pi.data;
+			if (ts->lexical_prob > papp->fun->ep->prob) {
+				ts->lexical_prob = papp->fun->ep->prob;
+			}
+			break;
+		}
+		}
+	}
+}
+
 static PgfTokenState*
 pgf_new_token_state(PgfConcr *concr, PgfToken tok, GuPool* pool)
 {
@@ -1576,6 +1615,11 @@ pgf_new_token_state(PgfConcr *concr, PgfToken tok, GuPool* pool)
 	ts->tok = tok;
     ts->lexicon_idx = gu_map_get(concr->leftcorner_tok_idx, 
                                  &tok, PgfProductionIdx*);
+	ts->lexical_prob = INFINITY;
+	PgfLexiconFn clo = { { pgf_parser_compute_lexicon_prob }, ts };
+	gu_map_iter(ts->lexicon_idx, &clo.fn, NULL);
+	if (ts->lexical_prob == INFINITY)
+		ts->lexical_prob = 0;
 	return ts;
 }
 
@@ -1969,6 +2013,12 @@ pgf_parser_init_state(PgfConcr* concr, PgfCId cat, size_t lin_idx, GuPool* pool)
 	return state;
 }
 
+void
+pgf_parser_set_beam_size(PgfParseState* state, double beam_size)
+{
+	state->ps->beam_size = beam_size;
+}
+
 void
 pgf_parser_add_literal(PgfConcr *concr, PgfCId cat,
                        PgfLiteralCallback* callback)
diff --git a/src/runtime/c/pgf/parser.h b/src/runtime/c/pgf/parser.h
index 6952d33ab..c4c394aad 100644
--- a/src/runtime/c/pgf/parser.h
+++ b/src/runtime/c/pgf/parser.h
@@ -67,6 +67,9 @@ pgf_parser_next_state(PgfParseState* prev, PgfToken tok,
  * the pool used to create \parse.
  */
 
+void
+pgf_parser_set_beam_size(PgfParseState* state, double beam_size);
+
 void
 pgf_parser_add_literal(PgfConcr *concr, PgfCId cat,
                        PgfLiteralCallback* callback);