diff --git a/backend/genesys/gl124.cpp b/backend/genesys/gl124.cpp
index 8f45e7f1b..af193a338 100644
--- a/backend/genesys/gl124.cpp
+++ b/backend/genesys/gl124.cpp
@@ -744,7 +744,7 @@ void CommandSetGl124::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
 
     DBG(DBG_info, "%s: total bytes to send to frontend = %zu\n", __func__,
         dev->total_bytes_to_read);
diff --git a/backend/genesys/gl646.cpp b/backend/genesys/gl646.cpp
index 4777fe2b7..ac6c6170d 100644
--- a/backend/genesys/gl646.cpp
+++ b/backend/genesys/gl646.cpp
@@ -818,7 +818,8 @@ void CommandSetGl646::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t) session.output_line_bytes_requested
+          * (size_t) session.params.lines;
 
     /* select color filter based on settings */
     regs->find_reg(0x04).value &= ~REG_0x04_FILTER;
diff --git a/backend/genesys/gl841.cpp b/backend/genesys/gl841.cpp
index 6ea4025c5..3b068d178 100644
--- a/backend/genesys/gl841.cpp
+++ b/backend/genesys/gl841.cpp
@@ -978,7 +978,7 @@ dummy \ scanned lines
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
     if (session.use_host_side_gray) {
         dev->total_bytes_to_read /= 3;
     }
diff --git a/backend/genesys/gl842.cpp b/backend/genesys/gl842.cpp
index 782a527d9..9663799f5 100644
--- a/backend/genesys/gl842.cpp
+++ b/backend/genesys/gl842.cpp
@@ -569,7 +569,7 @@ void CommandSetGl842::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
 }
 
 ScanSession CommandSetGl842::calculate_scan_session(const Genesys_Device* dev,
diff --git a/backend/genesys/gl843.cpp b/backend/genesys/gl843.cpp
index 785c5d791..d7909f5c7 100644
--- a/backend/genesys/gl843.cpp
+++ b/backend/genesys/gl843.cpp
@@ -1042,7 +1042,7 @@ void CommandSetGl843::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
   dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
 
     DBG(DBG_info, "%s: total bytes to send = %zu\n", __func__, dev->total_bytes_to_read);
 }
diff --git a/backend/genesys/gl846.cpp b/backend/genesys/gl846.cpp
index 7a680d17e..6db312ac1 100644
--- a/backend/genesys/gl846.cpp
+++ b/backend/genesys/gl846.cpp
@@ -659,7 +659,7 @@ void CommandSetGl846::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
 
     DBG(DBG_info, "%s: total bytes to send = %zu\n", __func__, dev->total_bytes_to_read);
 }
diff --git a/backend/genesys/gl847.cpp b/backend/genesys/gl847.cpp
index b849aa2eb..32ad2b126 100644
--- a/backend/genesys/gl847.cpp
+++ b/backend/genesys/gl847.cpp
@@ -625,7 +625,7 @@ void CommandSetGl847::init_regs_for_scan_session(Genesys_Device* dev, const Gene
     dev->session = session;
 
     dev->total_bytes_read = 0;
-    dev->total_bytes_to_read = session.output_line_bytes_requested * session.params.lines;
+    dev->total_bytes_to_read = (size_t)session.output_line_bytes_requested * (size_t)session.params.lines;
 
     DBG(DBG_info, "%s: total bytes to send = %zu\n", __func__, dev->total_bytes_to_read);
 }