diff --git a/arch/sim/src/sim/posix/sim_linuxi2c.c b/arch/sim/src/sim/posix/sim_linuxi2c.c
index 009f9fa672..8b62b6f53f 100644
--- a/arch/sim/src/sim/posix/sim_linuxi2c.c
+++ b/arch/sim/src/sim/posix/sim_linuxi2c.c
@@ -269,7 +269,7 @@ struct i2c_master_s *sim_i2cbus_initialize(int bus)
   struct linux_i2cbus_master_s *priv;
   char filename[20];
 
-  priv = (struct linux_i2cbus_master_s *)malloc(sizeof(priv));
+  priv = (struct linux_i2cbus_master_s *)malloc(sizeof(*priv));
   if (priv == NULL)
     {
       ERROR("Failed to allocate private i2c master driver");
diff --git a/arch/sim/src/sim/posix/sim_linuxspi.c b/arch/sim/src/sim/posix/sim_linuxspi.c
index 466ab40ce2..ba3c3a6e03 100644
--- a/arch/sim/src/sim/posix/sim_linuxspi.c
+++ b/arch/sim/src/sim/posix/sim_linuxspi.c
@@ -702,7 +702,7 @@ struct spi_dev_s *sim_spi_initialize(const char *filename)
 {
   struct linux_spi_dev_s *priv;
 
-  priv = (struct linux_spi_dev_s *)malloc(sizeof(priv));
+  priv = (struct linux_spi_dev_s *)malloc(sizeof(*priv));
   if (priv == NULL)
     {
       ERROR("Failed to allocate private spi master driver");