diff --git a/src/modulator.h b/src/modulator.h
index d7133e3..7d129ee 100644
--- a/src/modulator.h
+++ b/src/modulator.h
@@ -3,25 +3,27 @@
 #include "rds.h"
 #include "waveforms.h"
 
+#pragma pack(1)
 typedef struct
 {
 	float level;
-	uint8_t rdsgen;
+	uint8_t rdsgen : 2;
 } RDSModulatorParameters;
 
 typedef struct {
 	uint8_t bit_buffer[BITS_PER_GROUP];
-	uint8_t bit_pos;
+	uint8_t bit_pos : 7;
 	float sample_buffer[SAMPLE_BUFFER_SIZE];
-	uint8_t prev_output;
-	uint8_t cur_output;
-	uint8_t cur_bit;
+	uint8_t prev_output : 1;
+	uint8_t cur_output : 1;
+	uint8_t cur_bit : 1;
 	uint8_t sample_count;
 	uint16_t in_sample_index;
 	uint16_t out_sample_index;
 	RDSModulatorParameters params;
 	RDSEncoder* enc;
 } RDSModulator;
+#pragma pack()
 
 void Modulator_saveToFile(RDSModulatorParameters *emp, const char *option);
 void Modulator_loadFromFile(RDSModulatorParameters *emp);