diff --git a/include/pflib/lpGBT.h b/include/pflib/lpGBT.h
index ec969789b..b4f378ce4 100644
--- a/include/pflib/lpGBT.h
+++ b/include/pflib/lpGBT.h
@@ -190,6 +190,14 @@ class lpGBT {
                  bool strong_scl = true, bool strong_sda = true,
                  bool pull_up_scl = false, bool pull_up_sda = false);
 
+  /** Setup i2c bus speed
+      \param ibus Which I2C bus (0-2)
+      \param speed_khz I2C speed (appropriate values are 100, 200, 400, 1000)
+      Note that this really just stores the information on what speed to use in
+     a temporary variable
+   */
+  void setup_i2c_speed(int ibus, int speed_khz);
+
   /** Start an I2C read */
   void start_i2c_read(int ibus, uint8_t i2c_addr, int len = 1);
 
diff --git a/src/pflib/Bias.cxx b/src/pflib/Bias.cxx
index 45248a573..69d0346ee 100644
--- a/src/pflib/Bias.cxx
+++ b/src/pflib/Bias.cxx
@@ -25,6 +25,7 @@ MAX5825::MAX5825(std::shared_ptr<I2C> i2c, uint8_t addr)
 std::vector<uint8_t> MAX5825::get(uint8_t channel) {
   uint8_t cmd = (uint8_t)(MAX5825::CODEn | (channel & 0x07));
 
+  i2c_->set_bus_speed(100);
   std::vector<uint8_t> retval = i2c_->general_write_read(our_addr_, {cmd}, 2);
 
   return retval;
@@ -33,6 +34,7 @@ std::vector<uint8_t> MAX5825::get(uint8_t channel) {
 void MAX5825::set(uint8_t channel, uint16_t code) {
   uint8_t cmd = (uint8_t)(0xB0 | (channel & 0x07));
 
+  i2c_->set_bus_speed(100);
   std::vector<uint8_t> retval =
       i2c_->general_write_read(our_addr_,
                                {cmd, static_cast<uint8_t>((code << 4) >> 8),
@@ -58,18 +60,21 @@ Bias::Bias(std::shared_ptr<I2C> i2c_bias, std::shared_ptr<I2C> i2c_board) {
 
 void Bias::initialize() {
   // Reset all DAC:s
+  i2c_bias_->set_bus_speed(100);
   i2c_bias_->general_write_read(0x10, {0x35, 0x96, 0x30}, 0);
   i2c_bias_->general_write_read(0x12, {0x35, 0x96, 0x30}, 0);
   i2c_bias_->general_write_read(0x14, {0x35, 0x96, 0x30}, 0);
   i2c_bias_->general_write_read(0x18, {0x35, 0x96, 0x30}, 0);
 
   // Set internal ref on DAC to 4.096 V
+  i2c_bias_->set_bus_speed(100);
   i2c_bias_->general_write_read(0x10, {0x27, 0x00, 0x00}, 0);
   i2c_bias_->general_write_read(0x12, {0x27, 0x00, 0x00}, 0);
   i2c_bias_->general_write_read(0x14, {0x27, 0x00, 0x00}, 0);
   i2c_bias_->general_write_read(0x18, {0x27, 0x00, 0x00}, 0);
 
   // Set up the GPIO device MCP23008
+  i2c_board_->set_bus_speed(100);
   i2c_board_->general_write_read(0x20, {0x00, 0x70}, 0);
 
   // Turn on the status LED
@@ -88,6 +93,7 @@ void Bias::initialize() {
 }
 
 double Bias::readTemp() {
+  i2c_board_->set_bus_speed(100);
   i2c_board_->general_write_read(0x4A, {0x00}, 0);
   usleep(250);  // Response is a bit slow
   std::vector<uint8_t> ret = i2c_board_->general_write_read(0x4A, {}, 2);
diff --git a/src/pflib/lpGBT.cxx b/src/pflib/lpGBT.cxx
index 7f401f0af..fe0806048 100644
--- a/src/pflib/lpGBT.cxx
+++ b/src/pflib/lpGBT.cxx
@@ -594,6 +594,15 @@ void lpGBT::setup_i2c(int ibus, int speed_khz, bool scl_drive, bool strong_scl,
   if (speed_khz > 500 && speed_khz < 2000) i2c_[ibus].ctl_reg |= 0x03;
 }
 
+void lpGBT::setup_i2c_speed(int ibus, int speed_khz) {
+  if (ibus < 0 || ibus > 2) return;
+
+  i2c_[ibus].ctl_reg &= 0x80;  // keep the scl_drive
+  if (speed_khz > 125 && speed_khz < 300) i2c_[ibus].ctl_reg |= 0x01;
+  if (speed_khz > 300 && speed_khz < 500) i2c_[ibus].ctl_reg |= 0x02;
+  if (speed_khz > 500 && speed_khz < 2000) i2c_[ibus].ctl_reg |= 0x03;
+}
+
 static constexpr uint8_t CMD_I2C_WRITE_CR = 0;
 static constexpr uint8_t CMD_I2C_1BYTE_WRITE = 2;
 static constexpr uint8_t CMD_I2C_1BYTE_READ = 3;
diff --git a/src/pflib/lpgbt/I2C.cxx b/src/pflib/lpgbt/I2C.cxx
index 2aa7169a2..3590165c7 100644
--- a/src/pflib/lpgbt/I2C.cxx
+++ b/src/pflib/lpgbt/I2C.cxx
@@ -5,7 +5,7 @@ namespace lpgbt {
 
 void I2C::set_bus_speed(int speed) {
   ispeed_ = speed;
-  lpgbt_.setup_i2c(ibus_, speed);
+  lpgbt_.setup_i2c_speed(ibus_, speed);
 }
 
 int I2C::get_bus_speed() { return ispeed_; }